FOUS11 KWBC 090734
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
234 AM EST Mon Feb 9 2026

Valid 12Z Mon Feb 09 2026 - 12Z Thu Feb 12 2026

...Pacific Northwest through Northern Rockies... Day 1...

A shortwave trough crossing the area will be positioned atop the
interior Northwest to start the period, and then translate rapidly
eastward through D1. This feature will likely shear out into the
westerlies as it advects into the High Plains in response to rapid
ridging building in its wake, but there has been a subtle trend of
increased amplitude of this feature tonight. This shortwave will
work effectively with an intensifying upper jet streak to overlap
mid-level height falls with LFQ diffluence, leading to sufficient
ascent to produce a wave of low pressure along a cold front south
of the region.

Additionally, this jet streak will result in increasing mid-level
frontogenesis, especially within the 700-500mb layer, which will
produce impressive omega directly into the DGZ. Although ascent
will be temporally modest, cross-sections indicate a high threat
for CSI within any snow bands that develop, and this could (30-60%
chance) produce 1-2"/hr snowfall rates. The heaviest snowfall is
likely in the terrain of the Absarokas and near Yellowstone NP due
to upslope enhancement, but anywhere across southern MT and
northern WY could see bands of heavy snowfall which will accumulate
rapidly despite marginal thermals in the low- levels. The high-res
guidance has trended upward significantly, as have many of the
globals, so confidence has increased in significant snowfall
accumulations, which is now reflected by WPC probabilities that
indicate a high risk (>70% chance) for at least 4 inches, with more
than 12 inches possible in the higher terrain including the Lewis
Range and Tetons.

...Sierra Nevada to the Central Rockies... Days 2-3...

A closed mid-level low will approach central California from the
west on Tuesday before slowly filling into an open, positively
tilted trough Wednesday as secondary vorticity energy digs towards
Baja. This slow evolution will result in pronounced S/SW flow
aloft, which will combine with a strengthening jet streak to spread
moisture onshore CA and then expand eastward towards the Central
Rockies by late Wednesday. This prolonged, albeit relatively
modest, moisture plume/IVT will bring much needed precip to the
Great Basin and central Rockies through midweek.

Snow levels will be at or just below 7000ft along the Sierra Nevada
on Tuesday in the onshore flow, dropping to around 6000ft Tuesday
night under height falls. Great Basin/Rockies snow levels will
generally remain 6000-7000ft through midweek.

2-day snow probabilities from WPC suggest a near certainty (>90%)
of at least 8 inches across much of the Sierra with locally as much
as 2 feet possible (30% chance) in the higher Sierra. Additional
snowfall totals exceeding 8 inches are possible (50-70%) for parts
of the Uintas, Colorado Rockies, and northern CA ranges.

...Northern Great Lakes and Northeast... Days 1-3...

A closed mid-level low will elongate and track from the Northern
Great Lakes to across New England mid-week, exiting to the Gulf of
Maine by Thursday morning. This upper feature will be accompanied
by an extended vorticity lobe on its south side, helping to produce
strong ascent through height falls/PVA across the region. As this
develops, pronounced warm air advection (WAA) will develop to its
south as a surface low /clipper type/ races southeast beneath the
upper trough. This will produce two rounds of ascent: first with
the intensifying WAA south of the surface low, and then second with
post-clipper CAA/upslope flow.

While the ascent within the WAA will be impressive, it will also be
of short duration, generally 6-12 hours, so although snowfall rates
will likely be intense (50-70% chance of 1+"/hr), the total
snowfall accumulations will be tempered as reflected by WPC
probabilities that are around 30% for 4+ inches across the U.P. of
MI D1, and then 30-70% on D2 for Upstate NY and northern/central
New England. Despite that, some more significant snowfall
accumulations are likely across the Tug Hill Plateau, the
Adirondacks, and the Greens where a combination of CAA for lake
effect snow (in the Tug Hill) and upslope snow (Adirondacks and
Greens) will lengthen the duration of accumulating snowfall. In
these areas, locally more than 8 inches of snow is possible
(10-30%, highest across the Tug Hill Plateau).

Finally, as the closed low moves into the Gulf of Maine, a surface
low will deepen offshore in response. While direct impacts from
this surface low are not expected to be significant, the guidance
is hinting at a lingering inverted trough pivoting back across
coastal Maine Wednesday. These inverted troughs can sometimes lead
to sneaky-heavy snowfall accumulations, so although current WPC
probabilities are around 50-70% for 4+ inches of snow, this will
need to be monitored for any upticks as the event gets closer.


Weiss


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