FOUS11 KWBC 280807
QPFHSD
Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
307 AM EST Wed Jan 28 2026
Valid 12Z Wed Jan 28 2026 - 12Z Sat Jan 31 2026
...Great Lakes... Days 1-3...
The seemingly endless cyclonic flow that has kept the LES machine
cranking over snow belts of the Great Lakes looks to continue
through the remainder of the work-week. Frigid 850mb temperatures
will persist with temperatures around -18 to -24C, which are below
the 10th climatological percentile. According to GLERL, Lake Erie
is essentially ice covered, so available moisture will be limited
there while Lakes Superior and Ontario remain largely open. W-NWrly
low-level winds will continue today before the approach of a sharp
500mb shortwave pivots through and shifts winds more out of the
N-NNW by Thursday. Northerly flow continues Friday as high pressure
builds in over the Northern Plains. This northerly flow supports
the most likely area of heavy snow on Day 3 to be down wind of Lake
Michigan, potentially into the Chicago metro. 72-hour WPC
probabilities depict high chances (>70%) for snowfall totals >8"
over the eastern shores of Lake Superior in the Michigan U.P. and
down wind of Lake Ontario to the south of an over the Tug Hill. The
area with the best odds of seeing over a foot of additional snow
(most on Day 1) over the next few days are near the Oswego, NY area
where WPC probabilities for over a foot of snow are 10-20%. Day 3
probabilities down wind of Lake Michigan current depict moderate
probabilities 40-50% for at least 4" across the southwest shores of
Lake Michigan.
...Cascades & Olympics... Days 1-3...
A series of storm systems tracking into the Gulf of Alaska will
direct rounds of moisture and WAA at western WA through the
remainder of the week. Strong upslope flow should support locally
heavy snowfall totals as low as 4,000ft, but most heavy snow will
reside in the more remote areas above 5,000ft. Snow levels rise
from 4000 to 5000ft over the WA Cascades Wednesday through
Thursday. By Friday, snow levels approach 6,000ft by Friday in
western WA. WPC probabilities for >4" is moderate (40-70%) around
Stevens Pass, but lighter accumulations around Snoqualmie are
anticipated at this moment given the higher snow levels.
...Northern & Central Plains... Days 2-3...
A weak Pacific shortwave trough tracking NW-SE will ride along a
nearby 850mb front to support periods of snow from the northern
High Plains on south in the the central High Plains. Snow is not
expected to be overly heavy, although the Black Hills through
orographic lifting may be able to see snowfall amounts surpass 6".
This is supported in WPC probabilities which show moderate-to-high
chances (50-70%) for >4" of snow in the Black Hills, and low
chances (10-30%) in their peaks for >8". Elsewhere, from eastern MT
on south and east through the Missouri River Valley, most snowfall accumulations are likely to range between 1-3". Some hazardous
travel is possible, especially where roads temperatures are at or
below freezing in wake of the recent extreme cold.
...Southern Appalachians & Mid-Atlantic... Days 3...
...Confidence In Impactful Snowfall Increasing For the Southern
Appalachians and Southern Mid-Atlantic; Key Messages are linked at
the bottom of the discussion...
To say there remains a large amount of model spread in the
potential winter storm beyond Day 3 would be an understatement. In
the past 36-24 hours, ensemble guidance have flipped camps to
where the GEFS are the snowier members, CMCE are more in the
middle, and the EC-EPS are less snowy. It is worth noting that AI
ensemble membership are not as snowy as the GEFS, but show a little
more snow than the EC-EPS, making this an interesting test in how
the AI ensemble membership performs. However, within this overall
"cloud" of uncertainty, guidance is beginning to hone in on higher
chances for impactful snowfall across the Carolinas and southern
Virginia by the end of the Day 3 timeframe.
Regarding the setup-- WPC Cluster Analysis shows this potential
winter storm comes down to several factors: 1) strength of the
emerging Great Lakes shortwave trough. 2) speed of the shortwave
trough. 3) tilt/amplitude of the shortwave trough as it tracks
east. 4) Confluence strength near Nova Scotia. They all work
together in an intricate dance that makes for difficulties in
modeling. A stronger/slower shortwave can buy time for confluence
over New England and Nova Scotia to weaken, giving the shortwave
more time to amplify, and allow for closer storm tracks to the
coast that bring heavy snow as far west as the I-95 corridor (some
GEFS members and some CMCE members). Where the shortwave is
stronger but progressive, heavier snowfall occurs but largely
closer to the coast and as far west as the NC Piedmont (CMCE
members, UK ensembles, split EC/GEFS members). If the shortwave
trough is more progressive and cannot separate itself from the
larger TPV to the east there is less amplification, it results in
a flatter and more positively/tilted shortwave trough, and thus the
storm remains largely out at sea (EPS, EC-AIFS ensembles, some
GEFS/CMCE members). It is worth noting that, while the EC-AIFS has
largely performed well inside of 5 days much of the winter season,
the EC- AIFS and ECMWF did suppress the track of the most recent
winter storm too much ~4-5 days out before correcting northward
inside of 72 hours out.
In terms of storm analogs, this upper level setup and TPV
interaction does not appear like a common scenario to get a deep
upper low rapidly strengthening near the Southeast/Mid- Atlantic.
Most analog matches seem to get towards the closed upper low in
different ways or suppress the system altogether leaving little in
terms of precipitation. However, the 12z Tuesday CIPS Analogs (GFS-
based) highlighted the significant winter storm of March 1980 as
an interesting top match. This storm produced very heavy snowfall
across VA and eastern NC and can simply show the ceiling this type
of setup can have. Like what was previously mentioned, other
limited analogs are suppressed and show the very low floor that is
still possible. All ensemble systems GEFS/CMCE/EPS/EC- AIFS/AIGEFS
show this large spread as well.
Back to the current forecast. This setup is highly timing
dependent; from the primary shortwave trough currently east of
Hudson Bay, to the interaction/spacing of the 500mb cyclonic gyres
in southeast Canada and south of Iceland that promote the
confluence ahead of the potential storm, to the incoming Pacific
shortwaves that track into western Canada and adjust the
strength/position of the western North America ridge. There remain
a host of embedded shortwaves that will work together to create a
complex storm evolution off the East Coast. Whatever the current
model solutions show beyond 72 hours out is unlikely to be the
final product. Expect additional model changes in the coming days.
If there is an additional aspect to this storm that has increased
in confidence in the past 24 hours, it is the opportunity for
coastal flooding and beach erosion along the Mid-Atlantic coast.
The one thing they do agree on is this upper trough tracks through
the OH Valley Friday afternoon with sufficient PVA and 850-500mb
mean layer moisture to support snow from central KY to the southern Appalachians through Friday night. Then, the closing off of a 850mb
low seems plausible across the southern Appalachians Saturday
morning, which should help increase lift into the Carolina
Piedmont. WPC probabilities do show increasing chances for at least
minor accumulations >4" over eastern KY and northeast TN, while
there are low- chances (10-30%) for snowfall totals >4" through
early Saturday morning in the TN/NC Smokeys and Blue Ridge of NC.
Probabilities then begin to increase to 30-50% across central NC by
12z Saturday. Most snowfall associated with this system is
expected to occur after 12z Saturday, so be sure to check back for
the latest forecast as it enters the short range over the next few
days. Residents and those traveling to the Carolinas on north up
the East Coast will want to continue following the forecasts from
WPC and your local NWS WFO for the latest regarding this potential
winter storm.
The probability for significant icing is less than 10 percent.
Snell/Mullinax
...Extreme Cold (1) & Winter Storm (2) Key Messages are in effect.
Please see current Key Messages below...
https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_1.png
https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_2.png
$$
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* Origin: Capitol City Online (618:250/1)
