Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
433 AM EDT Sun May 3 2026

Valid 12Z Sun May 03 2026 - 12Z Wed May 06 2026

...Sierra Nevada...
Days 1-2...

Broad, not that deep upper low off CA will drift toward the SF Bay
area through tonight, then drift to SoCal through Tuesday when it
opens to a trough and ejects east. Modest moisture plume will
interact with the Sierra Nevada from the south with precip onset
expected this afternoon. Snow levels initially around 9000ft drop
to around 8000ft late tonight. Day 1 snow probs for >6" are around
20% in the High Sierra. The south movement of the low brings
some prolonged flow to the Sierra Nevada with snow levels down to
around 7500ft. Day 2 snow probs for >6" are 40-60% across the High
Sierra.


...Wyoming and Colorado...
Days 2/3...

Strong ridging north of the CA low will amplify over the northeast
Pacific into the Yukon through tonight and promote troughing to
surge down the Canadian Prairies tonight and the northern Plains
Monday. Meanwhile the SWly jet downstream of the CA low will surge
to the central Plains Monday, aiding left exit dynamics.
Precipitation will expand over southern WY and northern CO Monday
afternoon into Tuesday ahead of the cold front with high snow
levels initially >9000-10,000ft. On Tuesday, the cold front (and
precip focus) will push south through eastern CO with snow levels
lowering to 6000-7000ft behind the boundary that will dam up east
of the Divide, keeping snow levels >8000ft on the west side.
Modest to locally heavier snow should set up over parts of
southern WY through CO via easterly/upslope flow (e.g., Laramie
and Medicine Bow Mountains) with additional modest snow over the
Bighorns and Wind River Range through Tuesday evening before
tapering off as the focus shifts east onto the Plains Wednesday.
Day 2 snow probs for >6" are 20-30% on the Wind River Range and
Bighorns and 30-60% on the south Laramie and CO Front Range. Day 3
snow probs for >6" are nearly identical for the Wind River/Bighorn
with greatly expanded coverage over south WY through central CO
Ranges down to the northern Sangre de Cristos. Probs for >12" are
40-70% along the Front Range in what will be an impactful storm
though should be mainly seen as beneficial/drought relief.


The probability for significant icing over one-tenth of an inch is
less than 10 percent across the CONUS.


Jackson