Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
311 AM EDT Mon Apr 13 2026

Valid 12Z Mon Apr 13 2026 - 12Z Thu Apr 16 2026

...Sierra to the Rockies...
Days 1-2...

Lead upper trough over the Great Basin will briefly close off and
continue northeastward then eastward, spreading snow over the
northern Great Basin into Idaho and Montana/Wyoming. Accumulations
will generally be light.Trailing vorticity on the southwest side of
the lead trough will close off into an upper low over SoCal this
morning and move eastward. This will bring another round of snow to
the central/southern Sierra this afternoon/evening with light to
modest accumulation of a few inches to perhaps 6-8 inches at the
highest peaks. Tonight into tomorrow, this upper low will move into
the Four Corners region, enhancing snowfall more broadly over the
Wasatch, Uintas, and especially the San Juans in southwest CO. Snow
levels initially around 8000-9000ft will fall to around 7500ft by
later Tuesday and early Wednesday as most of the snow ends from
west to east. WPC probabilities for at least 6 inches of snow are
>50% above about 8000ft over eastern OR into the central ID ranges,
and above 10,000-11,000ft into the Wasatch, Uintas, and San Juans.


...Pacific Northwest/Northern Rockies...
Day 2-3...

Initial troughing over Alaska will steadily move southeastward
along the BC coast through Tuesday, bringing a 105kt jet into
western WA. A modest surge of moisture along/ahead of the cold
front (IVT values around the 90th percentile for mid-April) will
support widespread rain and mountain snow across the Cascades
starting around early Tuesday, becoming heavy Tuesday
afternoon/evening, and continuing as lighter snow into Wednesday.
Snow will spread eastward across the Northern Rockies Tuesday night
and into Wyoming by Wednesday. Snow levels initially around 3000ft
(Cascades) to 4000ft (Northern Rockies) will fall to around
1500-2000ft in the Cascades as much colder air works in from the
northwest by 12Z Wednesday and especially by 00Z Thursday (700mb
temperatures dropping to around -15C). Though precipitation may
start as rain, snow will quicklybecome the dominant p-type for most
passes. Some of this snow could even become significant at higher
passes, including Snoqualmie Pass and Washington Pass. By 12
Thursday, the upper trough will move inland, just past the
Cascades, ending snow from west to east just after the end of this
forecast period. Through 12Z Thursday, WPC probabilities for at
least 6 inches of snow are >50% above about 2500ft in the Cascades
and 5000-6000ft in the Northern Rockies. Probabilities for at least
a foot of snow are >50% above 3000-3500ft in the Cascades and
6000-7000ft in the Northern Rockies.


The probability of significant icing for days 1-3 across the CONUS
is less than 10 percent.

Fracasso/Miller