FOUS11 KWBC 190713
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
313 AM EDT Sun Apr 19 2026

Valid 12Z Sun Apr 19 2026 - 12Z Wed Apr 22 2026

...Upstate New York/Northern New England... Day 1...

Strong cold front pressing east beneath increasing mid-level
cyclonic flow will cross New England Sunday morning with rapid
temperatures drops in its wake on impressive CAA. Moisture
streaming northward ahead of the front will fall as rain, but as
temperatures cool dramatically, precipitation will change to snow,
especially in the higher terrain of the Adirondacks, Greens,
Whites, and highest elevations of western/northern Maine before a
slow end as the column dries tonight. WPC probabilities remain
around 30-50% for 4+ inches of snow across the higher elevations
of this region.

...California... Day 3...

Closed 500mb low will gradually translate east to come onshore
northern CA Tuesday aftn/eve. The guidance has been slowing with
this evolution over the past few model runs, but pronounced WAA
southeast of the core of this low will spread elevated IVT (>90%
chance of at least 250 kg/m/s and locally as high as 500 kg/m/s
according to the West-WRF) into CA late D2 into D3. This enhanced
IVT will moisten the column to result in widespread precipitation
as height falls and an accompanying Pacific jet streak move onshore
CA. Snow levels at precipitation onset will be 6000-7000 ft, but
should fall steadily beneath the upper low, becoming as low as 5000
ft by the end of the forecast period. However, steep lapse rates
beneath the upper low combined with strengthening ascent through
upslope flow, especially across the Sierra, may allow snow levels
to drop even further as reflected by NBM 10th% snow levels falling
below 4000 ft by 12Z Wednesday. While the heaviest accumulations
are expected to be above 5500 ft in the Sierra and Shasta/Trinity
region, some light accumulations are possible at these lower
elevations as well.

WPC probabilities for at least 8 inches of snow have climbed to
above 70% above 6000 ft in the Sierra and parts of the northern CA
terrain, and it is becoming likely that a warning-level snow event
will cause impact to travel across the Passes on Tuesday. After
coordination with the local WFOs, due to uncertainty in timing of
the event (as model trends have slowed) no hazards will be issued
yet, but it is likely in the next 1-2 model cycles winter storm
watches will be needed for the Sierra and possibly other
neighboring terrain as this event spreads northeast through mid-week.

The probability for significant freezing rain exceeding 0.1 inches
across the CONUS is less than 10 percent.

Weiss

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