Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
437 AM EDT Mon Apr 15 2024

Valid 12Z Mon Apr 15 2024 - 12Z Thu Apr 18 2024


...Utah and Colorado Mountains...
Days 1/2...

Upper low over Utah early this morning will shift east to Colorado
today with 1"/hr snow rates over the length of the Wasatch and
Uinta where Day 1 PWPF for >8" are 50-80% above the snow level that
rises from 6500' to 7500'.

By this evening, the heavy snow focus shifts east to the CO
Rockies thanks to a combination of the favored upper ascent and
aid from lee- side cyclogenesis over northeast CO. Moisture from
the Gulf will funnel into the northern and western CO Rockies
around this low with a primed upslope pattern within the terrain
over northern CO. PWPF for >8" encompasses much of this terrain
above 7500' with the probabilities between 50-80% in the Medicine
Bow and Park Ranges. Probs for >12" are within the aforementioned
area with probabilities of exceedance running between 30-60% with
best chances in the Front Range. Heavy snow in CO tapers to light
through Tuesday morning.


...Northern Rockies...
Days 2-3...

A positively-tilted trough will continue to shift southeast over
BC with downstream/lee-side flow allowing an inverted trough to
persist into Wednesday. The combination of strong surface ridging
providing prominent cold air advection for the season along with
the inverted trough will create a primed upslope enhancement over
the eastern portions of the northern Rockies late Tuesday night
into Wednesday, persisting over northern WY into Thursday. PWPF for
>6" is highest on Day 2.5 within the Absarokas over to the
Bighorns with values of 70-90%. In the Lewis Range/Glacier National
snow levels plummet (Falling 3500' to 1500' by Wednesday AM) due
to cold air advection regime and falling heights aloft.
Probabilities for at least 6" are between 40-60% for Glacier
National Park, and generally between 50-90% across those areas over
into Yellowstone over to the Bighorn Range by Tuesday evening.


The probability of significant icing is less than 10 percent.


Jackson