Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
436 PM EDT Wed Apr 24 2024

Valid 00Z Thu Apr 25 2024 - 00Z Sun Apr 28 2024


...The West...
Days 2-3...

The leading wave in a series of impulses approaches the PacNW coast
late tonight before amplification results in a broad longwave
trough digging to the Desert Southwest late Thursday through Friday
before shifting over the southern Rockies late Saturday. Moisture
surging inland ahead of this developing trough will lead to
widespread mountain snowfall over the Cascades and Intermountain
West Thursday night/Friday with snow levels dropping to 5000ft in
the Northwest and 7000ft over the Great Basin. Day 2 PWPF for >6"
snow is 40-80% in the higher OR Cascades and 30-60% in the ranges
of northeast NV, UT, and central ID/southwest MT.

The wave shifts east from the Desert Southwest Friday night,
closing off at H5 over the UT/AZ border before turning northeast to
central CO Saturday. This allows heavy snow to develop over the
southern through north-central Rockies (up through
Yellowstone/Absarokas) with lee-side cyclogenesis shifting moisture
from the Plains up over the WY then CO ranges. This storm motion
allows for little movement to inflow bands as they pivot, keeping
heavy snow over the Absaroka and Wind River Ranges before the focus
shifts more to the CO Rockies and perhaps out onto the High Plains
Saturday night/Sunday.

Day 3 PWPF for >8" are >80% for the Wind River Range where 1-2ft
seem likely and 40-80% from the central ID/MT ranges,
Absarokas/Bighorns, Uinta, and Park/Front Ranges and northern San
Juans in CO. Snow levels are generally 7000-8000ft over WY and
9,000ft over CO. One note is given the higher rates northwest of
the H7 low may lead to localized reductions is snow level.


The probability of significant icing is less than 10 percent.


Jackson