-
MESO: Heavy rain - floodi
From
Weather Alert@618:250/1 to
All on Wed May 19 16:48:00 2021
AWUS01 KWNH 192044
FFGMPD
LAZ000-ARZ000-200130-
Mesoscale Precipitation Discussion 0209
NWS Weather Prediction Center College Park MD
443 PM EDT Wed May 19 2021
Areas affected...Arkansas
Concerning...Heavy rainfall...Flash flooding possible
Valid 192042Z - 200130Z
Summary...Flash flooding is possible over portions of Arkansas
during the late afternoon and early evening as broad south to
southeast flow continues to draw moisture into the region.
Western and central portions of Arkansas received 2 to 5 inches of
rain last night/early this morning....making it more susceptible
to additional flooding concerns this evening.
Discussion...Convection over parts of Louisiana and Arkansas was
becoming more numerous and more capable of producing locally heavy rainfall..especially across the central portion of the state where
storms were developing on the nose of a 2.00 inch precipitable
water plume and where southeasterly flow was tapping an airmass
with MUCAPE values of 1000 to 1500 J per kg. Atfernoon VAD Wind
Profiles across the region show that the flow has backed and
accelerated to 25-35 kts at 850 mb since the 12Z soundings...and
that flow has been providing plenty of additional moisture
transport into the region. Flash flooding is possible wherever
convective activity occurs over areas of central and western
Arkansas which received 2 to 5 inches of rain last night/early
this morning.
Present indications are that the probability of rainfall exceeding
1 inch per hour should diminish shortly after 20/00Z as the lower
atmosphere begins to stabilize.
Bann
ATTN...WFO...JAN...LZK...SHV...
ATTN...RFC...ABRFC...LMRFC...NWC...
LAT...LON 36179213 35419128 33469137 32799252 33259324
34329346 35429333 35889299
$$
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From
Weather Alert@618:250/1 to
All on Thu May 20 16:10:00 2021
AWUS01 KWNH 201757
FFGMPD
MSZ000-LAZ000-ARZ000-TXZ000-202355-
Mesoscale Precipitation Discussion 0216
NWS Weather Prediction Center College Park MD
156 PM EDT Thu May 20 2021
Areas affected...Louisiana...Far Southeast Arkansas...Far Eastern
Texas
Concerning...Heavy rainfall...Flash flooding likely
Valid 201755Z - 202355Z
Summary...Flash flooding is likely this afternoon across much of
Louisiana, far southeastern Arkansas, and far eastern Texas with
rainfall rates increasing to 2-3"/hr. Additional accumulations are
expected to reach 3-6" where showers and thunderstorms train.
Discussion...Convective activity along the LA Gulf coast is
expected to increase this afternoon as SB CAPE ramps up to
1000-2000 J/kg amid peak solar insolation. An exceptional moist
air mass remains in place with PWATs ranging from 1.75-2.00
inches, at or above the 90th climatological percentile for
surrounding WFOs. Efficient low-level moisture transport from the
Gulf will continue with a 25-35 kt 850 mb jet over the region.
Mid- to upper-level forcing continues to be the limiting factor at
play today, but the highly moist and unstable air mass within a
corridor of persistent low-level confluence will keep excessive
rain potential elevated.
The latest radar trends and hi-res CAM guidance suggest that the
ongoing convection across southeastern Louisiana this morning will
begin to shift westward into west-central Louisiana and
neighboring portions of Arkansas and Texas. As instability
increases, expect hourly rainfall rates to increase to the
2-3"/hour range. Training of these rates will allow for 3-6"
totals across an already highly saturated area. 3-hr FFG values
are less than 3 inches across the highlighted area, and even less
than 2 inches across much of Sabine River basin (from Port Arthur,
TX to near Shreveport, LA). Therefore hydrologic sensitivity is
quite high, as NASA SPoRT 0-40 cm soil moisture anomalies exceed
the 90th percentile.
Churchill
ATTN...WFO...JAN...LCH...LIX...SHV...
ATTN...RFC...LMRFC...WGRFC...NWC...
LAT...LON 33519411 33099197 31289109 30149019 28999106
29689384 31529419
$$
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From
Weather Alert@618:250/1 to
All on Sun May 23 18:36:00 2021
AWUS01 KWNH 232046
FFGMPD
TXZ000-240000-
Mesoscale Precipitation Discussion 0225
NWS Weather Prediction Center College Park MD
445 PM EDT Sun May 23 2021
Areas affected...south/southeast Texas
Concerning...Heavy rainfall...Flash flooding possible
Valid 232039Z - 240000Z
Summary...A persistent south-southeasterly flow regime will
continue to support showers and a few thunderstorms across the
discussion area this evening along with a risk of flash flooding.
Discussion...A persistent, deep south-southeasterly flow regime
continues between the southwestern periphery of a mid/upper ridge
centered over the Mid-South and a weak mid-level vort max centered
about 100 mi E of Brownsville. The flow pattern is continuing to
support a very moist, weakly buoyant airmass across the discussion
area with 2-2.2 inch PW values and 1000-1500 J/kg MUCAPE. The
airmass is weakly capped, and subtle lift associated with the
mid-level vort max and weak/subtle boundary layer confluence
continues to support areas of showers with embedded thunderstorms.
A couple of bands of heavier precipitation exist from near
Gonzales to Victoria, Texas and across the western Houston Metro
area, with enhanced rainfall rates of near 1-2 inches per hour
noted in the western-most band near Gonzales.
This persistent precipitation regime is expected to continue for
at least the next 3 hours or so as southeasterly low-level flow
maintains very moist low-level air and the mid-level vort max is
very slow to move. This will allow for occasional/isolated bands
of heavier precipitation to fall in areas that have received
abundant rainfall over the past week - exceeding 15 inches in a
few spots. The precipitation is resulting in wet soils and
correspondingly low flash flood guidance as a result (as low as 1
inch-per-hour thresholds near PSX/VCT). Additionally, showers and
isolated thunderstorms currently offshore (east of the mid-level
vort max) will migrate inland into the discussion area over the
next 2-3 hours. Most CAMs suggest a downtick in precipitation
rates after around 00Z or so, and the risk of additional flash
flooding will be re-evaluated around that time.
ATTN...WFO...CRP...EWX...FWD...HGX...
ATTN...RFC...WGRFC...NWC...
LAT...LON 30819714 30719608 30209510 29629472 29049495
28459619 28379715 28799794 29199814 29829821
30279811 30599783
$$
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From
Weather Alert@618:250/1 to
All on Tue May 25 19:40:00 2021
AWUS01 KWNH 251918
FFGMPD
TXZ000-260115-
Mesoscale Precipitation Discussion 0236
NWS Weather Prediction Center College Park MD
317 PM EDT Tue May 25 2021
Areas affected...Eastern TX
Concerning...Heavy rainfall...Flash flooding possible
Valid 251915Z - 260115Z
SUMMARY...Showers and thunderstorms with heavy rainfall rates may
pose some flash flood threat over the next few hours.
DISCUSSION...The latest radar imagery shows a long-lived MCS now
bowing into areas of eastern TX. The airmass out ahead of this
over the broader southeast TX coastal plain is quite moist and
unstable with PWs of 1.8 to 2 inches and MLCAPE values locally
over 2000 j/kg. Meanwhile, a southerly low-level jet of 30 kts is
in place ahead of the MCS.
This favorable thermodynamic environment downstream of the MCS
suggests the ongoing activity will continue to expand off to the
east with some upside potential to expand in coverage and gain
greater convective organization given the additional
destabilization of the boundary layer that is expected over the
next couple of hours due to solar insolation.
Dual-pol radar QPE has already been suggesting some 1.5+ inch/hr
rainfall rates, and these rates should continue within the
stronger cells over the next few hours given the efficient
moisture transport pattern. The radar imagery also shows scattered
heavy showers and thunderstorms developing ahead of the main
complex within the moist/unstable low-level flow with locally
enhanced rain rates.
Over the next few hours, the southern portion of the long-lived
MCS may begin to slow its advance off to the east and may tend to
become oriented more southwest/northeast in nature such that
individual cells may begin to train over the same area. This
coupled with some cell-merger potential will tend to increase the
threat for some excessive rainfall totals going through the
late-afternoon and early evening hours.
The latest HRRR guidance suggests at least locally 3 to 4+ inch
rainfall totals going through 00Z. Given the wet antecedent
conditions, and heavy short-term rainfall rate potential, there
will be at least some concern for flash flooding.
Orrison
ATTN...WFO...FWD...HGX...LCH...SHV...
ATTN...RFC...WGRFC...NWC...
LAT...LON 31999435 31759401 31279389 30589444 30069531
30079603 30289639 30439657 30589667 30799673
30999656 31409561 31949499
$$
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From
Weather Alert@618:250/1 to
All on Thu May 27 16:50:00 2021
AWUS01 KWNH 271708
FFGMPD
MOZ000-ARZ000-OKZ000-KSZ000-272305-
Mesoscale Precipitation Discussion 0245
NWS Weather Prediction Center College Park MD
105 PM EDT Thu May 27 2021
Areas affected...Northeast OK...Southeast KS...Southwest MO...Far
Northwest AR
Concerning...Heavy rainfall...Flash flooding likely
Valid 271705Z - 272305Z
Summary...Scattered areas of flash flooding will be likely across
portions of the Southern Plains this afternoon as deep convection
blossoms within a broad unstable warm sector. Hourly rainfall
rates of 2-3" are expected with 6-hr localized accumulations of
4-6 inches possible where convection trains.
Discussion...A broad warm sector characterized by MUCAPE of
2000-4000 J/kg, PWATs of 1.6-1.9 inches, and significant deep
layer moisture convergence will foster rapid upscale growth of
convection across the Southern Plains this afternoon as a potent
mid-level shortwave digs southeastward from the Northern Plains.
Semi-discrete thunderstorms will initially be relatively slow
(15-20 kts) with 2-3"/hr rainfall rates quickly saturating soils.
Much of the highlighted area is already in the 60-90th percentile
of 0-40 cm soil moisture (via NASA SPoRT Land Info System data),
indicating somewhat vulnerable antecedent hydrologic conditions.
Given that the latest high-res CAM guidance (including the HRRR)
has continued to handle convective trends rather poorly,
confidence in any targeted specific area is somewhat low. Where repeating/training of convection can occur 2-3" hourly rates will
rapidly translate to localized totals of 4-6 inches. Some
preference is given to northeastern Oklahoma to realize the
highest rainfall totals, but this area is also where 6-hr FFG is
the highest (3-5 inches). While southeast Kansas in particular has
the lowest FFG (2-4 inches), less repeating of convection is
likely as the advancing cold front cuts off avaliable instability.
That said, the combonation of a highly favorable mesoscale
enviorment and relatively poor hydrologic conditions make
localized flash flooding likely over the broader region.
Churchill
ATTN...WFO...EAX...ICT...LSX...LZK...OUN...SGF...TOP...TSA...
ATTN...RFC...ABRFC...LMRFC...MBRFC...NWC...
LAT...LON 39059479 38889350 38389241 36129320 35379462
35469789 37119753 37999677 38519579
$$
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From
Weather Alert@618:250/1 to
All on Tue Jun 1 16:41:00 2021
AWUS01 KWNH 011904
FFGMPD
MSZ000-LAZ000-ARZ000-TXZ000-012300-
Mesoscale Precipitation Discussion 0263
NWS Weather Prediction Center College Park MD
303 PM EDT Tue Jun 01 2021
Areas affected...Eastern TX...Southern AR...North/Central LA
Concerning...Heavy rainfall...Flash flooding possible
Valid 011900Z - 012300Z
Summary...Showers and thunderstorms will continue to blossom
across eastern TX into southern AR and much of LA through the
afternoon. Some of this activity will be slow moving and with the
potential for training over the same areas. Therefore, rain rates
in excess of 2 inches/hour are possible with areal average
rainfall of 2-4+ inches possible through the next six hours.
Antecedent conditions combined with high resolution model signals
suggest flash flooding is possible.
Discussion...A mid/upper level trough across the central U.S. will
continue to provide modest divergence aloft. This combined with
shortwave activity (including an eastward advancing MCV in
northeastern TX) will lead to large scale forcing for ascent. In
response, rich Gulf moisture will be pulled north into eastern TX
and the Lower MS Valley region ahead of a stationary surface
boundary. As a result, precipitable water values of 1.5-1.75
inches will expand east and increase with strong WAA. Despite
morning cloud debris from earlier convection, MUCAPE has already
climbed above 2000 J/kg with additional destabilization expected
over the next several hours. Given these factors, anticipate
convection will continue to develop and blossom within this
region. Based on the propagation vectors and mean wind,
anticipate convection to be slow moving initially with the
potential for brief training. It should also be noted that with
weak shear of around 25 knots, highly organized convection is not
expected but possible across portions of eastern LA by later this
afternoon. According to high resolution guidance, rain rates may
exceed 2 inches/hour with areal average precipitation of 2-4+
inches within the next six hours. This is supported by the higher
HREF probabilities.
While flash flood guidance values within this region are fairly
high (3-5 inches in 3 hours), portions of the ArkLaTex region has
observed above normal precipitation over the past week along with
slightly above normal soil moisture within the scalloped region.
Therefore, scattered flash flooding may occur.
Pagano
ATTN...WFO...HGX...JAN...LCH...LZK...SHV...
ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...
LAT...LON 34449293 33279115 31199173 30109333 30069533
30649632 31599495 33329448
$$
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From
Weather Alert@618:250/1 to
All on Thu Jun 3 15:35:00 2021
AWUS01 KWNH 031556
FFGMPD
VAZ000-NCZ000-SCZ000-032154-
Mesoscale Precipitation Discussion 0270
NWS Weather Prediction Center College Park MD
1155 AM EDT Thu Jun 03 2021
Areas affected...NC/SC
Concerning...Heavy rainfall...Flash flooding possible
Valid 031554Z - 032154Z
Summary...Convection is rapidly expanding in coverage across
portions of the Carolinas, with isolated to scattered flash
flooding possible through the afternoon hours.
Discussion...Broadly confluent flow in the low levels, along with
the upper trough to the west and a subtle wave moving into the SC
coast are all helping initiate convection across SC/NC. The
scattered to widespread nature of convection will probably cap the
amount of destabilization possible...although still looking at
1000-2000 J/kg of CAPE, certainly sufficient for deep convection.
PWs are approaching 2", which is getting close to the early June
maximum expected values. Merging moisture plumes, one in the
mid/upper levels associated with the approaching trough, and the
other in the lower levels off the Atlantic, are supporting the
deep moist profiles. The combination of high PWs, high wetbulb
zero heights, and thin CAPE profiles certainly supports efficient
rainfall in any heavier cells through the afternoon hours.
The area is currently in drought conditions, although heavy rain
yesterday has saturated the top levels of soil in parts of the
region...while the deeper soil anomalies generally remain below
average. So while the region could generally still use more
rain...the saturated top layers of soil should help increase
runoff today resulting in isolated to scattered instances of flash
flooding. Cells will be quick moving off to the northeast, but
unidirectional flow supports some small linear training segments,
and some repeat of cells through the afternoon given the scattered
to widespread nature of convection.
Thus while a more widespread/organized convective complex seems
unlikely, the above ingredients should be enough to still result
in pockets of flash flooding through the afternoon hours. Urban
and low lying areas will be most susceptible...but some flash
flooding is possible wherever todaty's heavier totals overlap with
yesterdays.
Chenard
ATTN...WFO...AKQ...CAE...CHS...GSP...ILM...MHX...RAH...
ATTN...RFC...MARFC...SERFC...NWC...
LAT...LON 36737652 36407642 35557699 34747755 34497808
34047898 33587939 33427980 33358015 33588039
34218065 34718054 35757932 36517791
$$
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From
Weather Alert@618:250/1 to
All on Tue Jun 8 15:20:00 2021
AWUS01 KWNH 081557
FFGMPD
MAZ000-VTZ000-CTZ000-NYZ000-NJZ000-PAZ000-082156-
Mesoscale Precipitation Discussion 0300
NWS Weather Prediction Center College Park MD
1157 AM EDT Tue Jun 08 2021
Areas affected...northeastern Pennsylvania into southern New York
State
Concerning...Heavy rainfall...Flash flooding possible
Valid 081556Z - 082156Z
Summary...Slow-moving storms will pose a risk for isolated flash
flooding through the afternoon and early evening in and near the
discussion area.
Discussion...A slow-moving cluster of convection has evolved in
northeastern Pennsylvania over the past hour or so, with areas of
towering cumulus across much of the discussion area from
southeastern Pennsylvania to western Massachusetts. The storms
are in an environment characterized by weak, but westerly vertical
shear and very strong instability (as high as 4000 J/kg SBCAPE in
areas downstream of ongoing storms). The pre-convective airmass
is quite moist also, with PW values of 1.6 to 1.9 inch areawide.
Lift from an approaching shortwave trough across central PA/NY and
weak/subtle boundary layer confluence was also providing ascent
aloft for thunderstorm development.
Latest observations/guidance suggests that this mainly diurnally
driven convective activity will continue to expand in coverage
this afternoon. Local rainfall rates of 1-2 inches per hour have
already been observed beneath convective cores, and this will
expand in coverage with time - especially as storms form mature
cold pools and propagate slowly eastward. Flash flood guidance
values are in the 0.75-1.5 inch-per-hour range, which should be
easily exceeded beneath heavier convective cores/clusters. The
threat should wane some after sunset with loss of
heating/surface-based instability.
Cook
ATTN...WFO...ALY...BGM...BOX...CTP...OKX...PHI...
ATTN...RFC...MARFC...NERFC...NWC...
LAT...LON 43057325 42817261 42157246 41557285 40927380
40337472 40037588 40107668 40307712 40607717
42347608 42697525 43017412
$$
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From
Weather Alert@618:250/1 to
All on Tue Jun 8 15:21:00 2021
AWUS01 KWNH 081911
FFGMPD
OHZ000-MIZ000-INZ000-082315-
Mesoscale Precipitation Discussion 0302
NWS Weather Prediction Center College Park MD
311 PM EDT Tue Jun 08 2021
Areas affected...Northwest OH...Northeast IND...Ext Southwest MI.
Concerning...Heavy rainfall...Flash flooding possible
Valid 081910Z - 082315Z
SUMMARY...Slow moving cells and deepening moisture profiles
support localized heavy rainfall and potential for flash
flooding...
DISCUSSION...GOES-E WV suite denotes older shortwave/closed low
feature over the Tri-State area of S MI/NW OH/NE IND. Given its
placement in the larger scale pattern, upper level flow is
favorable for solid diffluence to support the developed convection
in/east of the UL proper. CIRA LPW suite also denotes moisture
entering the low to middle profile of the cells to further enhance
the rainfall efficiency, resulting in 1.75 to 1.9" of total
moisture in the column. Entrainment with 15-20kts of flow through
85-7H brings rates to 2-2.25"/hr, though equally allows for slow
cell motions and with upstream inflow and upstream propagation to
further slow motions. Strongest overshooting top near Hancock
county, OH seems to be ideally situated for this combination of
favorable upper-level divergence to show signs of building back
against the flow slightly. Development is enhanced by solid low
level convergence along Lake enhanced boundaries intersecting with
the weak northward march of the higher Td air from the
Ohio/Mississippi Valleys.
While the area is generally below average in the longer terms...
there is lower FFG values across the area of concern which aligns
with with AHPS 2-week anomalies near to 200% of normal. Hourly
FFGs of 1-1.5" and 3hr values of 1.5-2.5" have solid potential to
be exceeded with these cores. But given the nature of the complex
overall coverage should be scattered in nature and will dissipate
with reducing instability into the evening. As such, flash
flooding is considered possible but local thunderstorms of 2-3"
totals in 1-2 hours or even sub-hourly per report near Vermilion.
Gallina
ATTN...WFO...CLE...DTX...ILN...IWX...
ATTN...RFC...NCRFC...OHRFC...NWC...
LAT...LON 42358328 41698290 41558155 41128142 40638193
40448272 40538339 40938435 41008536 41398551
41748465
$$
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From
Weather Alert@618:250/1 to
All on Wed Jun 9 14:40:00 2021
AWUS01 KWNH 091505
FFGMPD
TNZ000-ALZ000-MSZ000-ARZ000-092102-
Mesoscale Precipitation Discussion 0312
NWS Weather Prediction Center College Park MD
1104 AM EDT Wed Jun 09 2021
Areas affected...northern Mississippi, eastern/southeastern
Arkansas, northwestern Alabama
Concerning...Heavy rainfall...Flash flooding likely
Valid 091502Z - 092102Z
Summary...Areas of flash flooding remain likely across the
discussion area through at least 21Z. Significant impacts are
expected given extreme antecedent rainfall over the past 24 hours.
Discussion...Recent radar mosaic imagery indicates several bands
of slow-moving/propagating convection across the discussion area -
particularly in eastern Arkansas, northern Mississippi (near
Oxford), and northern Alabama (northwest of Birmingham). The location/orientation of these bands isn't particularly surprising
given broadly confluent westerly/southwesterly 850mb flow
partially orthogonal to a weak low-level boundary from near Little
Rock to near Tupelo. The low-level flow was maintaining a moist,
destabilizing pre-convective airmass across the region
(characterized by 2-inch PW values, nearly 2000 J/kg MUCAPE, and
minimal convective inhibition). The moisture and instability was
promoting rainfall rates of up to 3 inches per hour beneath
heavier thunderstorm cores which easily exceed FFG thresholds in
the region - especially in eastern Arkansas and northern
Mississippi where widespread areas of 3-10 inches of rainfall were
observed yesterday. Impressive MRMS Flash responses have already
been noted this morning in east-central Arkansas and near Oxford,
Mississippi.
Though the general axes of convergence are less focused compared
to yesterday, models/observations generally suggest that bands of
heavy rainfall will continue to propagate slowly
eastward/east-southeastward resulting in very heavy rainfall and
additional accumulations of at least 2-4 inches (locally higher)
through 2030Z. Models also indicate initiation of convection
south of these bands, which isn't surprising given the strong
destabilization occurring there. Localized training of convection
is expected in this regime (which may already be materializing in
east-central Arkansas). Convective mergers may also allow for a
slow, more southward component to MCS motions during the period as
well, allowing for heavier precipitation to eventually shift
toward the US82 corridor in Mississippi. Each of the
aforementioned factors point to locally significant flash flooding
especially beneath heavier/training convection.
Cook
ATTN...WFO...BMX...HUN...JAN...LZK...MEG...OHX...
ATTN...RFC...ABRFC...LMRFC...SERFC...NWC...
LAT...LON 35068996 35018783 34828659 34608618 34118614
33568659 33268805 33139020 33109190 33399234
34059232 34689205 34949122
$$
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From
Weather Alert@618:250/1 to
All on Wed Jun 9 14:42:00 2021
AWUS01 KWNH 091732
FFGMPD
NYZ000-PAZ000-WVZ000-OHZ000-092331-
Mesoscale Precipitation Discussion 0314
NWS Weather Prediction Center College Park MD
132 PM EDT Wed Jun 09 2021
Areas affected...Virginia, northern North Carolina
Concerning...Heavy rainfall...Flash flooding possible
Valid 091731Z - 092331Z
Summary...Convection drifting slowly southward across the
discussion area could pose a very localized/isolated flash flood
risk through peak-heating hours..
Discussion...Satellite/lightning imagery indicates scattered
thunderstorms across the discussion area that were moving slowly south-southwestward. The cells were in an environment
characterized by very weak vertical wind shear (with northerly
flow around 10 knots or so from the surface to 300mb), moderate
instability (around 2000 J/kg MLCAPE), and PW values ranging from
1.3-1.7 inch. These conditions are conducive for brief heavy
downpours with as much as 1 inch per hour of rainfall in a few
spots. FFG values of around 1.5 inch-per-hour rainfall rates
(slightly lower in southern New York State and southwestern
Pennsylvania) suggest that a brief/isolated flash flood risk will
exist - particularly in areas where heavier rainfall occurs over
flood-prone or hydrophobic surfaces (i.e., urban areas and hilly
terrain). This risk should be mainly dirunally driven and lessen
after sunset.
Cook
ATTN...WFO...BGM...BUF...CLE...CTP...PBZ...
ATTN...RFC...MARFC...NERFC...OHRFC...NWC...
LAT...LON 42317939 42297756 41927676 41567661 40907664
40347684 39847756 39977979 40688129 41208142
41688113
$$
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From
Weather Alert@618:250/1 to
All on Thu Jun 10 14:24:00 2021
AWUS01 KWNH 101620
FFGMPD
NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-102215-
Mesoscale Precipitation Discussion 0321
NWS Weather Prediction Center College Park MD
1219 PM EDT Thu Jun 10 2021
Areas affected...portions of the northern Mid-Atlantic region
Concerning...Heavy rainfall...Flash flooding likely
Valid 101616Z - 102215Z
SUMMARY...Slow moving thunderstorms are expected to increase in
coverage across the northern Mid-Atlantic region this afternoon.
Rainfall rates of 1-2 in/hr will be common, but locally higher
rates can not be ruled out.
DISCUSSION...Visible satellite imagery through 1545Z showed an
expanding cumulus field within an otherwise mostly clear
environment across the Delmarva Peninsula into MD and southeastern
PA. A few showers and thunderstorms have also popped up on
regional radar imagery over northern Delaware Bay and along the
Catocin Mountains of northern MD into the Appalachian chain of
southern PA. PWATs within the pre-convective environment are 1.7
to 2.0 inches and 850-200 mb mean-layer flow is very weak across
the entire region at less than 10 kt, which will support slow
storm motions. Little CIN on the 12Z soundings from WAL and IAD
suggest storm coverage will continue to increase with daytime
heating with the front and local terrain acting as sources for
lift. In addition, locally stronger easterly flow just behind the
cold front may help to support near-stationary convection along
the terrain of northern VA into northwestern MD and southern PA.
Given the lack of speed shear with height, storms should not be
organized in nature or long-lasting, but they should be rather
efficient with rainfall production given high wet bulb zero
heights of roughly 13 kft. Rainfall rates of 1-2 in/hr are very
likely with localized rainfall rates up to 3 in/hr possible. In
fact, rainfall rates from the HRRR support 1-2 inches of rain in
15 to 30 minutes which seems reasonable given the moist
environment. Portions of the Delmarva into southern MD and
southeastern PA received heavy rainfall yesterday and will be more
susceptible to localized flash flooding today. While flash
flooding is not expected to be widespread across the entire
region, scattered to numerous slow moving thunderstorms will
produce heavy rainfall with several areas at risk for flash
flooding, including the urban I-95 corridor from south of D.C.
into northern DE with 2-4 inches expected through 22Z.
Otto
ATTN...WFO...AKQ...CTP...LWX...PBZ...PHI...
ATTN...RFC...MARFC...OHRFC...NWC...
LAT...LON 40587854 40517767 40357679 40047594 39547543
38187496 37767548 37877657 39167880 39907971
40507942
$$
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From
Weather Alert@618:250/1 to
All on Thu Jun 10 14:25:00 2021
AWUS01 KWNH 101727
FFGMPD
MSZ000-LAZ000-ARZ000-102315-
Mesoscale Precipitation Discussion 0322
NWS Weather Prediction Center College Park MD
127 PM EDT Thu Jun 10 2021
Areas affected...central AR into northeastern LA and central MS
Concerning...Heavy rainfall...Flash flooding likely
Valid 101722Z - 102315Z
SUMMARY...Backbuilding and training convection is expected to
continue areas of flash flooding for central MS and northeastern
LA, expanding northwestward into central AR through early evening.
Peak rainfall rates of 2-3 in/hr should continue and the overlap
with recent areas of heavy rain will exacerbate ongoing flooding.
An additional 3-5 inches is forecast through 23Z.
DISCUSSION...A long-lived complex of thunderstorms over the Lower
Mississippi Valley has shown a slow evolution over the past 6
hours toward the south and west. Low level cloud elements on
visible imagery continue to show a confluent pattern into the
tri-state region of AR/LA/MS where MRMS rainfall estimates ending
at 17Z have been near 4 in/hr in Issaquene County. A lack of
rainfall observations in the area has made it difficult to confirm
MRMS estimates, but the history of this complex and the efficient
environment make the MRMS rates seem reasonable. MLCAPE estimates
as of 17Z show 2000-3500 J/kg over northern LA into central AR
where mostly clear skies have allowed surface temperatures to
climb into the upper 80s while dewpoints are in the mid to upper
70s.
While winds at 850 mb have weakened since earlier this morning
into the 10-20 kt range, similar strength and direction of the
850-300 mb mean flow has supported backbuilding of storms into
southeastern AR. Short term forecasts from the RAP have been
consistent with maintaining the current strength and direction of
the low and mid-level flow into the early evening. Therefore, weak
to locally moderate low level confluent flow within the moist
environment and the presence of the right-entrance region of a
40-60 kt upper level jet streak to the north should continue to
support convective development over the next several hours.
Ongoing training near the LA/AR/MS junction may weaken in the next
2-3 hours in favor of increasing development into a expanding
cumulus field over central AR. The greatest confidence for an
additional 3-5 inches of rain exists across far western MS into
northeastern LA and southern AR, while convection to the north
(centarl AR) is expected to be more scattered in nature with
rainfall rates of 1-2 in/hr. Given heavy rain over the past 3
days, additional any added heavy rain will only worsen ongoing
flooding concerns.
Otto
ATTN...WFO...JAN...LZK...MEG...SHV...
ATTN...RFC...ABRFC...LMRFC...NWC...
LAT...LON 35689213 35289148 34019055 33468979 33018917
32418911 32098970 32089100 32769240 33579289
34879299 35589275
$$
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From
Weather Alert@618:250/1 to
All on Thu Jun 10 14:26:00 2021
AWUS01 KWNH 101802
FFGMPD
MDZ000-VAZ000-WVZ000-OHZ000-KYZ000-102300-
Mesoscale Precipitation Discussion 0323
NWS Weather Prediction Center College Park MD
201 PM EDT Thu Jun 10 2021
Areas affected...WV...southwest OH...Western & Southwestern VA...
Concerning...Heavy rainfall...Flash flooding possible
Valid 101800Z - 102300Z
SUMMARY...Slow/Chaotic motions but ample deep warm cloud layer for
efficient rainfall through complex terrain.
DISCUSSION...GOES-E WV and Visible suite depict a vertically
sheared cyclone with 6.2um channel centered over western VA, 7.3
over central WV and IR/VIS channels showing compact center into
southwest OH. As a result, there is weak chaotic flow regimes,
though low level through 7H suggests southwesterly moist flow
across E WV into the front ranges of the Appalachians in western
VA and this is denoted well in the 850-7H Layer PW from CIRA.
Being on the western periphery of the upper-level waves has
supported some additional clearing for ample isolation and
building of instability. Mtn/Valley circulation combined with
some low level mass piling is supporting increasing agitation of
cu field both under the best mid-level cooling/upper-low but also
along the southeast quadrant of the lower circulation along/near
the Ohio River. Mid-level cloudy conditions have all but rendered
areas across far N WV into the western MD/Eastern WV panhandle
less conducive.
Deepest convective elements are forming with the better mid-level
lapse rates along the terrain of far E KY into W VA. Still, due
to deep warm cloud layer, ample moisture individual cells will be
highly efficient with up to 2"/hr rates. Cell motions will be
near zero further north and west with 5-10 kts toward the NNE
across southern portions of the MPD area. Hi-Res CAMs all suggest
best scattered 2-2.5" totals over E WV into W VA with the slightly
better 5-10 kts of inflow to help maintain updrafts more than the
"up and splat" nature further north and east,
propagating/regenerating along the outflows.
Still both modes have solid potential to exceed the low FFG in
complex terrain which is about 1"/hr though lower values of
.5-.75"/hr are nearer the low level cyclone convergence point.
Flash flooding is likely though it will be highly
scattered/locally focused to only a few watersheds...where some
neighboring watersheds may miss out totally.
Gallina
ATTN...WFO...JKL...LWX...MRX...PBZ...RLX...RNK...
ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...NWC...
LAT...LON 39598200 39578099 39458008 39277949 39047903
38157928 37377979 36738086 36788232 37348272
38158231 39158235
$$
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From
Weather Alert@618:250/1 to
All on Sat Jun 19 10:23:00 2021
AWUS01 KWNH 191152
FFGMPD
FLZ000-GAZ000-ALZ000-MSZ000-191800-
Mesoscale Precipitation Discussion 0352
NWS Weather Prediction Center College Park MD
751 AM EDT Sat Jun 19 2021
Areas affected...southern Alabama, western Florida Panhandle,
southeastern Mississippi
Concerning...Heavy rainfall...Flash flooding likely
Valid 191149Z - 191800Z
Summary...An axis of focused convergence just east of the center
of TS Claudette will promote areas of flash flooding in the
discussion area (southeastern Mississippi through the Florida
Panhandle) through at least mid-day.
Discussion...Latest observations/mesoanalysis shows an area of
focused low-level convergence across southwestern Alabama and
vicinity coincident with intense convective development. The
storms themselves are in a very moist/buoyant environment with PW
values of 2.1-2.4 inches and 2000 J/kg MLCAPE values - highest
nearer the coast. The airmass is promoting extremely efficient
rainfall rates of 2-3.5 inches per hour near the strongest
convection - including within a dominant convective band near
Mobile this morning and with scattered cells ahead of the band
that will move northward into and through the discussion area from
open Gulf waters. 2-4 inch rainfall totals have already been
noted in southeastern Mississippi/southern Alabama - with
localized instances of totals nearing 8 inches since midnight CDT.
Although the specific evolution of convective bands within this
regime is somewhat uncertain, models and observations generally
suggest that the axis of greatest low-level convergence will
gradually shift eastward along the north-central Gulf Coast within
the discussion area through 18Z or so. With strong buoyancy and
moisture located near/just offshore, intense updrafts and
convective bands will continue to persist in the discussion area,
with highest rainfall rates (exceeding 3 inches per hour at times)
exceeding any flash flood guidance thresholds. Flash flooding is
most likely to occur beneath any heavier bands and/or training
convection that can materialize and persist in the discussion
area.
It is worth noting that additional heavy precipitation may develop
west of the dominant convective band near Mobile Bay through the
afternoon depending on redevelopment of low-level confluence axes
near/east of the cyclone center. This can foster repeating
convection over areas that received precipitation in western
portions of the discussion area.
Cook
ATTN...WFO...BMX...FFC...JAN...LIX...MOB...TAE...
ATTN...RFC...LMRFC...SERFC...NWC...
LAT...LON 32498667 32448540 32088505 31118503 30168518
29898534 30048559 30238612 30198703 30038784
30038868 30208903 31118936 31758940 32198916
32438819
$$
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From
Weather Alert@618:250/1 to
All on Sat Jun 19 18:08:00 2021
AWUS01 KWNH 191721
FFGMPD
FLZ000-GAZ000-ALZ000-192318-
Mesoscale Precipitation Discussion 0355
NWS Weather Prediction Center College Park MD
120 PM EDT Sat Jun 19 2021
Areas affected...southeastern Alabama, Florida Panhandle, and
southwestern Georgia
Concerning...Heavy rainfall...Flash flooding likely
Valid 191718Z - 192318Z
Summary...Slow-moving convection on the southeastern periphery of
Tropical Cyclone Claudette will continue a risk of flash flooding
especially in the Florida Panhandle and vicinity through 00Z.
Discussion...Most of the heaviest convection on the southeastern
periphery of Claudette has been confined to one or two dominant
convective bands over the past 6 hours or so. The bands are
focused along a strongly confluent low-level wind field, which has
supported ascent within a very moist (2.2+ inches PW) and unstable
(2000+ J/kg MLCAPE) environment, allowing for areas of 2-3.5
inch-per-hour rainfall rates at times. The bands have produced
widespread areas of 2-5 inches of rain and isolated amounts as
high as 7.5. The highest amounts have so far been confined to
land areas nearer the stronger instability (located within 100 mi
of the coast and areas offshore).
These trends should continue through the evening hours.
HRRR/HREF/Nam and other guidance suggests that at least one or two
bands of convection should persist or gradually become more
elongated from southwest to northeast across the discussion area.
The localized training of convection will continue to allow for
widespread heavy rain to shift eastward, with many areas of 2-5
inch rainfall (and locally higher amounts) to occur across the
discussion area. The rainfall rates have overwhelmed flash flood
guidance (especially in flood-prone areas) and resulted in flash
flood impacts - especially in the Pensacola area recently.
Cook
ATTN...WFO...BMX...FFC...JAX...MOB...TAE...
ATTN...RFC...SERFC...NWC...
LAT...LON 32648425 32248332 31328294 30888307 30418348
30178409 29738512 29638587 30128700 30968719
31748690 32298635 32508549
$$
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From
Weather Alert@618:250/1 to
All on Sat Jun 19 18:08:00 2021
AWUS01 KWNH 192023
FFGMPD
ILZ000-MOZ000-200112-
Mesoscale Precipitation Discussion 0356
NWS Weather Prediction Center College Park MD
423 PM EDT Sat Jun 19 2021
Areas affected...PORTIONS OF EASTERN MISSOURI AND WESTERN
ILLINOIS...INCLUDING THE ST LOUIS METRO AREA
Concerning...Heavy rainfall...Flash flooding possible
Valid 192012Z - 200112Z
Summary...A west-northwest to east-southeast area of back-building
convection along an axis of favored low-level frontogenesis will
result in an enhanced risk of flash flooding through 01Z.
Discussion...At 20Z, a surface cold front was draped across
northern Missouri and northwest Illinois. With the uptick in
pre-frontal south-southwesterly flow in the lower levels, the
airmass south of this front continues to destabilize this
afternoon as per satellite and radar trends, particularly across
portions of northeast and east-central Missouri where mixed-layer
CAPES average between 3000-4000 j/kg per the latest SPC
mesoanalysis. At the same time, the deep-layer moisture pooling is
also helping to raise PWAT values (1.6 to 1.8+ inches currently).
Albeit subtle, the position of the outlook area southwest of a
departing northern stream shortwave is resulting in weak
divergence aloft, with the focused area of deep-layer lift and
low-level frontogenesis aiding to the initiation of convective
clusters across portions of northeast and eastern Missouri into
western Illinois. As the afternoon progresses, the convection is
expected to grow upscale and expand across the outlook area,
particularly across portions of northeast and eastern Missouri
along the axis of greatest deep-layer instability. Given the
favorable thermodynamical environment, hourly rainfall rates of
2-2.5 inches are anticipated underneath the strongest cells, which
may lead to localized flash flooding, particularly in urban and
other areas prone to flash flooding. The latest CAM guidance
indicates pockets of 3-5" totals through 01Z over the outlook
area. Given the likely expansion of the convection upstream
(toward the axis of maximum instability), along with the
southeasterly storm motions, some cell training is expected,
thereby giving credence to these higher amounts indicated by the
CAMs.
Hurley
ATTN...WFO...ILX...LSX...PAH...
ATTN...RFC...LMRFC...MBRFC...NCRFC...NWC...
LAT...LON 39819149 39729003 39348896 38488894 38028992
38399102 38999196 39559205
$$
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From
Weather Alert@618:250/1 to
All on Sun Jun 20 07:45:00 2021
AWUS01 KWNH 201001
FFGMPD
FLZ000-GAZ000-ALZ000-201500-
Mesoscale Precipitation Discussion 0364...Corrected
NWS Weather Prediction Center College Park MD
601 AM EDT Sun Jun 20 2021
Corrected for Changed Areas Affected
Areas affected...Florida Panhandle, Southeast AL, Southwest GA
Concerning...Heavy rainfall...Flash flooding possible
Valid 200951Z - 201500Z
Summary...Expanding coverage of thunderstorms in warm advection
ahead of an MCV will create an increasing flash flood risk this
morning. Multiple rounds of convection with rain rates to 2"/hr
are possible. Rainfall of 1-3" with isolated higher totals is
expected.
Discussion...A potent MCV stemming from a long-lasting forward
propagating MCS which has raced eastward overnight is now lifting
E/NE east of Hastings, NE. This MCV is being driven in part by a
robust and amplifying mid-level shortwave, and is moving into a
tropical airmass characterized by PWs around 1.5" and MUCape of
1500-2500 J/kg. A stationary front was analyzed draped west to
east along the MO/IA border, and recent VWPs indicate the 850mb
LLJ is increasing to 25-35 kts from the SW. This low-level SW flow
is isentropically ascending the stationary front, leading to
locally enhanced ascent across the region.
As the MCV continues to move eastward, ascent through PVA ahead of
the parent shortwave, isentropic upglide, low-level convergence
along the nose of the LLJ, and some enhanced acceleration east of
the MCV should maximize into the favorable thermodynamics. Recent
reflectivity from KEAX and KOAX indicate convection expanding
rapidly within the WAA regime and organizing due to bulk shear of
25-35 kts, with radar-estimated rainfall rates of 1-2"/hr becoming
common. While mean 850-300mb winds are robust to the E/NE at 20-30
kts, several rounds of heavy rainfall are possible during the next
few hours.
The HREF hourly rain probabilities suggest rainfall rates of 1-2"
will remain common through 12Z before beginning to wane as the MCS
moves into subtly drier air and the LLJ begins to veer, weakening
the ascent. During this time, rainfall of 1-3" is likely in many
locations as shown by the high-res guidance, and 6-hr HREF EAS
probabilities for 1" are above 60%, indicating both the agreement
of the members and the potential for excessive rainfall. While
recent rainfall has been modest during the past 14-days leading to
drier than normal soil moisture, there have been pockets of
rainfall 150% of normal during this time frame in SW IA. Here, FFG
is locally reduced to 1.5-2"/3hrs, and exceedance probabilities
are as high as 50%. Isolated flash flooding is possible through
early morning, but is most likely should this heavy rainfall occur
atop these locally more saturated soils.
Weiss
ATTN...WFO...BMX...FFC...JAX...MOB...TAE...
ATTN...RFC...SERFC...NWC...
LAT...LON 32888426 32808366 32508303 32078261 31648242
31058232 30588228 30238243 29958259 29708287
29528332 29428379 29448447 29498495 29668553
29878601 30138625 30498637 31068626 31558597
32118552 32568511 32778480
$$
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From
Weather Alert@618:250/1 to
All on Sun Jun 20 19:06:00 2021
AWUS01 KWNH 201923
FFGMPD
NCZ000-SCZ000-210122-
Mesoscale Precipitation Discussion 0366
NWS Weather Prediction Center College Park MD
323 PM EDT Sun Jun 20 2021
Areas affected...portions of North and South Carolina
Concerning...Heavy rainfall...Flash flooding possible
Valid 201922Z - 210122Z
Summary...Gradually increasing convective coverage could result in
a few areas of flash flooding this afternoon and evening.
Discussion...Ahead of the eventual path of TD Claudette, strong
insolation amid a moist and increasingly buoyant airmass
(characterized by 2-2.3 inch PW values and around 2000 J/kg
MLCAPE) was fostering robust convective development recently. The
storms are in an environment with southwesterly flow aloft and
were moving northeastward at around 15-20 knots. However, the
weak low-level confluence and orientation of the development was
allowing for convection to repeat/develop in areas that have
received around 1-3 inches of rain earlier and have FFG values
ranging from 1-2 inch-per-hour thresholds. The very moist airmass
was allowing for rainfall rates to exceed these thresholds beneath
the heavier updrafts (up to around 2.5 inches per hour at times),
suggesting that at least a spotty flash flood threat should
materialize especially wherever training convection can occur.
Over time, convective coverage should continue to increase through
at least sunset due to continued insolation and low-level
convergence ahead of Claudette. There may be a downtick in
convective coverage thereafter due to loss of insolation, although
the moist environment should still sustain a few lingering storms
after sunset especially where updrafts can ingest non-convectively
modified air.
Cook
ATTN...WFO...AKQ...CAE...CHS...GSP...ILM...MHX...RAH...
ATTN...RFC...SERFC...NWC...
LAT...LON 36507687 35757645 35247670 34627730 33947811
33447893 32747988 32568062 32898137 33258164
34078207 34768161 35558024 36197842
$$
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From
Weather Alert@618:250/1 to
All on Mon Jun 21 15:39:00 2021
AWUS01 KWNH 211917
FFGMPD
VAZ000-WVZ000-OHZ000-TNZ000-KYZ000-220116-
Mesoscale Precipitation Discussion 0371
NWS Weather Prediction Center College Park MD
316 PM EDT Mon Jun 21 2021
Areas affected...Central/Eastern Kentucky...Central Appalachians
Concerning...Heavy rainfall...Flash flooding possible
Valid 211916Z - 220116Z
Summary...Training thunderstorms along and ahead of a cold front
will be capable of producing hourly rain totals of 1-2" at times
and could lead to flash flooding across portions of the lower Ohio
Valley and central Appalachians through early evening.
Discussion...Large scale forcing for ascent provided by the
approach of a shortwave trough is focused over portions of the
lower Ohio Valley into the central Appalachians this afternoon. At
the surface, a seasonably strong cold front is analyzed generally
along/north of the Ohio River. The environment ahead of this
feature is very warm and moist, characterized by dewpoints in the
lower to middle 70s with a recently GPS analyzed PW of 1.6-1.8".
There is more than sufficient amounts of instability available
given both the surface heating and low/mid level lapse rates. The
latest SPC mesoanalysis showed MLCAPEs of 2000-2500 J/kg.
Current radar imagery shows an organizing line of thunderstorms
congealing just ahead of the cold front, maximized with the better
low level convergence. This activity is moving east/northeast and
is aligned fairly well with the mean flow, suggesting an increased
potential for training/backbuilding. Recent radar imagery also
shows potential for some 1.5 to near 2" hourly totals and this
aligns with the recent HREF probabilities which peak between
19-23Z for the greatest potential for reaching these intense rain
rates. Total amounts through 00Z could reach localized 3-4".
These storms will be moving across areas more susceptible to flash
flooding with low water spots and terrain and could lead to flash
flooding. 14-day rainfall departures for eastern KY and WV are
much above normal with higher than normal soil moisture
saturation. The HREF shows modest probabilities of exceeding the
12Z FFG, 20-40 percent, through the afternoon, particularly across
eastern KY into far western/southwest WV.
Taylor
ATTN...WFO...ILN...JKL...LMK...OHX...PAH...RLX...RNK...
ATTN...RFC...LMRFC...OHRFC...NWC...
LAT...LON 38928055 37878041 37138296 36688463 36188772
37298756 38098454 38598263
$$
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From
Weather Alert@618:250/1 to
All on Mon Jun 28 19:41:00 2021
AWUS01 KWNH 282100
FFGMPD
MDZ000-VAZ000-WVZ000-290100-
Mesoscale Precipitation Discussion 0405
NWS Weather Prediction Center College Park MD
459 PM EDT Mon Jun 28 2021
Areas affected...West Virginia...Ext Western MD...
Concerning...Heavy rainfall...Flash flooding possible
Valid 282100Z - 290100Z
SUMMARY...Numerous pulse thunderstorms with rain rates and
sub-hourly totals of 1.5-2.5" pose possible isolated flash
flooding conditions.
DISCUSSION...Deeper moisture/instability across the Cumberland
Plateau is sloshed up into the higher terrain of the central WV
Appalachians with weak upslope and southwesterly flow pushing the
tight gradient in moisture into the area of concern. Deeper mean
layer flow is highly confluent across the 850-7H layer on the
western periphery of a sharp anticyclonic flow. Upslope flow from
the east as well, provided sufficient surface moisture convergence
to initiate a line of pulse to weakly organized convection. LPW
aslo denotes the main updraft core from 850-5H is about 1.1"
indicative of high moisture. Given modest flux convergence may
result in rates of 2-2.25"/hr. Given complex terrain, these
hourly totals have the potential to exceed 1 hour FFG values
particularly across central to northeast WV where the values are
less than 2". Outflow is likely to kick off additional cells
perhaps even cells eastward...and with mean deep layer flow
generally north-northwest to north-northeast, there may be some
repeat tracks that would further increase the potential to even
exceed 3hr FFG values which are generally below 2.5". Currently
threat is from Webster toward Randolph county but should expand
both northeast and southwest with time along with the overall
general propagation of the current cells toward the
north-northwest through the remainder of daylight hours before
remaining instability wanes.
Gallina
ATTN...WFO...LWX...PBZ...RLX...RNK...
ATTN...RFC...MARFC...OHRFC...NWC...
LAT...LON 39667953 39577886 39147877 38617937 38048067
37478179 37958233 38918137 39548051
$$
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From
Weather Alert@618:250/1 to
All on Mon Jun 28 19:42:00 2021
AWUS01 KWNH 282316
FFGMPD
ILZ000-MOZ000-290500-
Mesoscale Precipitation Discussion 0408
NWS Weather Prediction Center College Park MD
716 PM EDT Mon Jun 28 2021
Areas affected...Southwest to Central IL...
Concerning...Heavy rainfall...Flash flooding possible
Valid 282315Z - 290500Z
SUMMARY...Cycles of highly efficient but generally short-lived
thunderstorms traversing saturated ground conditions pose highly
scattered but likely flash flooding through early overnight hours.
DISCUSSION...Moisture streaming out of the western Gulf along the
western perimeter of deep sub-tropical high across the South surge
into proximity of the deep layer positive-tilt trof that has
dominated the Central U.S. for days. Ample deep moisture remains
pooled just southeast of the mean trof axis along/southeast of a
surface stationary front with near/over 2" total PWats extending
from southern Lake Michigan to southeast KS. While overall
thermal profiles continue to warm with lessening lapse rates day
by day, peak solar angle is sufficient to heat the surface
conditions to support SBCAPEs of 3000 J/kg within the warm sector.
Weak but sufficient 15-20kts of LLJ advect the unstable air into
proximity of weak mid to upper level impulses to support scattered
convective development across the same general axis.
Once again, an active cycle is blossoming across Central MO with
numerous cells breaking out with tops cooling below -60C.
However, winds are weak and each cell may only cycle with one or
two overshooting updrafts before weakening and becoming more
stratiform in nature. So peak rates of 2.5"/hr are common and may
be in close proximity to other cells, given deep layered
unidirectional steering flow, there are some occasional repeats
within a 2-3 hour period to support isolated 3-4" totals. The
real concern here is the axis of development remains stationary
over days so ground conditions are fully saturated with NASA SPoRT
LIS 0-40cm ratios generally over 90% from SE KS to NW IND...with
pockets of near 100% very common through that axis. As a result
FFG values are likely to be exceeded (less than 1.5"/hr and
2"/3hr) across much of MO into SW IL. There is greater distance
between instability and moisture axis across NE IL into IND, and
so many hi-res CAMs led by recent HRRRs suggest development to
remain in proximity to MO and SW IL through the evening and
overnight hours. ARW solutions have been poorer and FV3-LAM has
been worst performing through the afternoon to help in trying to
pinpoint any specific area/county within the area of concern.
Gallina
ATTN...WFO...DVN...EAX...ILX...LSX...SGF...
ATTN...RFC...ABRFC...LMRFC...MBRFC...NCRFC...NWC...
LAT...LON 40759026 40678900 39818865 39148941 38379055
37339246 37049333 37019418 37359456 38509435
39439316
$$
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From
Weather Alert@618:250/1 to
All on Wed Jun 30 16:31:00 2021
AWUS01 KWNH 301750
FFGMPD
PAZ000-WVZ000-OHZ000-302249-
Mesoscale Precipitation Discussion 0418
NWS Weather Prediction Center College Park MD
149 PM EDT Wed Jun 30 2021
Areas affected...Southeast OH and Southwest PA
Concerning...Heavy rainfall...Flash flooding possible
Valid 301749Z - 302249Z
SUMMARY...Recent radar and satellite trends indicate the potential
for isolated flash flooding across portions of southeast OH, far
northern WV and southwestern PA through mid afternoon.
DISCUSSION...Latest surface observations and visible satellite are
detecting a southwest to northeast oriented convergence axis from
southeast OH into southwest PA. Convection has rapidly developed
along this axis over the past hour or two. Meanwhile we have also
been tracking an intense small convective cluster as it tracks
across southeast OH. The motion of this convective cluster should
take it along the aforementioned convergence axis....resulting in
a narrow axis of potential training over the next few hours.
The environment is characterized by MLCAPE over 2000 J/kg and PWs
around 1.75"...plenty sufficient for heavy rainfall rates. Latest
MRMS data indicates instantaneous rainfall rates of around 4" in
the heavier activity. Thus it would only take relatively brief
training to get rainfall amounts approaching 2" in under an hour.
Soil conditions over most of the MPD area are at well below normal
saturation levels. So this region is not in an overly susceptible
position for flash flooding. It will likely take some training to
result in any flooding...and even at that it will most likely stay
confined to any more susceptible low lying or urban areas.
Nonetheless the latest radar/satellite representation does suggest
a small scale training risk over this area over the next couple
hours resulting in the aforementioned localized flash flood risk.
Chenard
ATTN...WFO...CTP...PBZ...RLX...
ATTN...RFC...MARFC...OHRFC...NWC...
LAT...LON 41107881 40877845 40507878 40017973 39678050
39548139 40148167 40388150 40728060 40957974
$$
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