Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
429 AM EDT Mon Apr 24 2023

Valid 12Z Mon Apr 24 2023 - 12Z Thu Apr 27 2023

...Northern/central Rockies...
Days 1-3...

A small upper low moving into western Washington this morning will
continue southeastward into southwestern ID this afternoon behind
a surface cold front. From the Blue Mountains eastward across
central ID to southwestern MT, snow will expand through the day as
the height falls move through and lower-level
convergence/frontogenesis combines with upslope into the terrain
along/east of the Divide where WPC probabilities of at least 6
inches are moderate (>40%). The cold front will continue into
Wyoming this evening with light to modest snow, especially in the
Tetons, pushing into northwestern CO by early Tuesday.

Closed low at 500mb will track southeastward across southwestern
CO while the 700mb low will traverse the center of the state,
beneath a broad area of upper divergence. Farther east, influx of
moisture northward out of the western Gulf will stream into CO
from the east as colder air filters in late Tuesday and especially
overnight. Forecast soundings indicate a well-saturated column
with strong UVVs through the DGZ in the mountains (esp above
7500ft) where snow will likely fall at 1-3"/hr Tuesday
evening/overnight into the Front Range. Snow levels will drop
below 6000ft, with accumulating snow increasing over the Palmer
Divide as well. WPC probabilities for at least a foot of snow are
high (>70%) above 9000ft and are moderate (>40%) for at least 4
inches above 7000ft. Into Wednesday, the upper low is forecast to
move steadily into northeastern NM as snow winds down from north
to south through the day. Most of the snow on D3 will be over
south central CO across the Sangre de Cristos and the Raton Mesa.
Additional snowfall is forecast to be only a few inches. Total
snowfall over the higher peaks in the Front Range may exceed 1-2
ft with potentially moderate to major impacts per the WSSI.

The probability of significant icing greater than 0.25" is less
than 10 percent.


Fracasso