Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
137 PM EST Sun Mar 1 2026

Valid 00Z Mon Mar 02 2026 - 00Z Thu Mar 05 2026

...Central Plains to Tennessee Valley...
Day 1...

Weak shortwave traversing through generally zonal flow from the
Central Plains to the Southern Appalachians will create a period of
modest ascent across the region. Subtle height falls along the
low-level baroclinic gradient associated with a stalled cold front
will help develop a wave of low pressure, and as this low pressure
tracks eastward along the front it will enhance a swath of
precipitation around it. Despite the weak nature of this surface
low, downstream warm and moist advection will intensify on 850mb
winds surging out of the Gulf, transporting moisture and a warm
nose northward, with increasing isentropic upglide leading to an
expansion of precipitation. The column is marginally supportive of
winter p-types, so while some areas will begin as snow, especially
from northern MO through southern OH, the advance of the warm nose
will result in mostly rain or freezing rain as the system
translates eastward through Monday afternoon. Total snowfall is
expected to be minimal at less than 2". However, WPC probabilities
indicate a 50-70% chance of at least 0.01" of ice, with some
locally higher totals approaching 0.1" for NW MO and north-central
KY/southern IN as reflected by significant spread in the WSE plumes
across these areas.


...Mid-Atlantic to Northeast...
Day 2-3...

An amplifying mid-level trough ejecting out of the Great Basin
will track steadily eastward Monday night through Tuesday, leading
to a surface low formation that will track along a wavering warm
front/stationary front draped eastward through the Mid-Atlantic. As
this low moves east in conjunction with its parent trough,
downstream height rises will occur through intensifying WAA, with
the resulting overrunning/upglide leading to an expansion of
precipitation from the Mid-Atlantic/Central Appalachians into the
Northeast/New England, especially as PWs surge to above the 90th
climatological percentile according to NAEFS. With Canadian high
pressure quickly retreating to the E/NE ahead of this system, the
warm nose accompanying the WAA will be able to surge quickly
northeast, and this will likely result in a rapid transition from
snow at precip onset, to a mix of sleet/freezing rain, and
eventually rain, even as far north as southern New England. Before
that transition, some impactful winter weather is likely through
briefly heavy snow (although accumulations should be modest) and
the icy sleet/freezing rain combination which will lead to some
impactful ice accumulations in the higher elevations of the
Central Appalachians and neighboring valleys where CAD signatures
remain prevalent through Tuesday morning.

WPC probabilities for snow exceeding 2" each day exceed 30% only in
a few isolated areas, the higher Central Appalachians D1, the
Greens and Berkshires on D2, and coastal/Downeast Maine on D3.
Total snowfall may reach 4" in a few of these areas.

The icing is expected to be more impactful, especially in the
Central Appalachians, where the probability for at least 0.1" of
ice exceeds 50-70% in the higher elevations of the Alleghenies, the
Blue Ridge of VA, and into the Laurel Highlands of PA. Locally as
much as 0.25" is possible in isolated locations. More widespread
icing exceeding 0.01" is expected from far NW NC through southern
New England, including the I-95 corridor from Washington, D.C.
through New York City where the Tuesday commutes could be impacted
by light icing and mixed precipitation.


...Central Rockies...
Days 1-2...

A potent closed low emerging from the Pacific will cross onshore CA
late tonight and then continue eastward across the Great Basin and
into the Central Rockies by Tuesday morning. Although this feature
is now progged to weaken as it translates eastward, it will still
maintain sufficient amplitude to drive robust height falls/PVA into
the Central Rockies, which when combined with a modest (80-90kts)
jet streak placed favorably into the Central Plains, will result in
lee cyclogenesis Monday evening. This low will deepen at least
marginally as it advects E/SE into Tuesday, while downstream
moisture
from the Gulf gets wrapped cyclonically into the system to create
anomalous PWs as high as the 97th climatological percentile. The
combination of synoptic ascent with upslope enhancement
north/northwest of the surface low will create areas of heavy snow,
especially above 7000 ft in the Uintas, Tetons, Wind Rivers,
Laramie Range, and across much of the CO Rockies including the Park
and Front Ranges. In these areas, WPC probabilities are high (>70%)
for at least 4" D1 in NW WY, expanding to include the terrain of
UT and CO on D2. Locally as much as 10" of snow is possible in the
higher terrain.


...Pacific Northwest...
Day 3...

An amplifying shortwave trough positioned well of the Pacific
Northwest coast will gradually advect eastward, coming onshore
Wednesday morning. As this shortwave moves onshore, it will produce
impressive height falls which will overlap with the RRQ of a
meridionally strengthening jet streak (downstream of the primary
trough axis) to drive pronounced deep layer lift into the
Northwest. At the same time, confluent flow immediately ahead of
the mid-level trough will gradually back to be more SW, pumping
elevated IVT onshore to provide the moisture needed for heavy
precipitation. There remain considerable differences among the
various models as to the intensity of this IVT, with the ECENS
suggesting a higher than 80% chance of at least 250 kg/m/s, which
is close to the West-WRF probabilities, while the GEFS shows almost
no IVT at all. Hedging towards the more aggressive guidance
indicates that this should result in periods of heavy snow,
especially in the Olympics, Cascades, and Northern Rockies, with
snow levels falling steadily from around 5000 ft to 4000 ft
beneath the upper trough and a corresponding cold front. WPC
probabilities D3 are high (>70%) for at least 4" of snow along the
spine of the Cascades of OR and WA, the highest terrain of the
Olympics, and parts of OR/ID/MT from the Blue Mountains through the
Sawtooth Region and into the far Northern Rockies near Glacier NP.


Weiss