Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
351 PM EDT Tue Apr 25 2023

Valid 00Z Wed Apr 26 2023 - 00Z Sat Apr 29 2023

...Colorado Rockies...
Day 1...

A winter storm will continue to impact the CO Rockies tonight into
Wednesday with significant accumulations mainly on the eastern
slopes to the Continental Divide. Mid-level closed low shifting
southeast to the Four Corners this afternoon. Deep moisture
flowing northward out of the western Gulf of Mexico will turn to
the west into the Front Range/Rockies have brought precipitable
water values to near 0.50" along the I-25 corridor. 700mb flow
will increase out of the east across the High Plains by this
evening with increasing snow rates of 1-3"/hr likely in heavier
bands due to strong surface convergence and upslope enhancement.
Saturated column and strong upward vertical velocities may help to
bring the snow level a bit lower through the Foothills as surface
temperatures cool to the low 30s past sunset. By Wednesday
morning, the upper low is forecast to be over northeastern NM with
snow starting to wind down from north to south and some
accumulations shifting through Raton Pass into northern NM.

Heaviest axis of snowfall will be along and east of the Divide
owing to easterly upslope enhancement, where 1-3ft are likely
above 8000ft. However, even over the San Juans, nearly under the
path of the upper low, amounts over six inches are likely. Thermal
profile east of the Foothills becomes less clear with temperatures
in the low to mid 30s with rain over the Plains and rain ending as
some snow in between. Higher elevations like the Palmer Divide
will also see appreciable snow but this will increase over the
Raton Mesa and especially the Sangre de Cristos as well, which
will see snow continue Wednesday morning. Day 1 WPC snowfall
probabilities of at least 12 inches of snow are high around Pikes
Peak, the Wet Mountains west of Pueblo, and the northern Sangre de
Christos.


...Rocky Mountains...
Days 2/3...

A mid-level shortwave is forecast to dive southeastward out of
Canada late Wednesday night, tracking south down the Rockies
through Friday in response to building upper ridging over the
Pacific Northwest. This will drive a cold front southward with a
drop in temperatures behind it and rain changing to snow for many
areas in its wake. Northerly to northeasterly flow post-FROPA will
favor the Bighorns and Black Hills were several inches of snow are
possible with Day 2 snow probabilities moderate for 4"+ there,
increasing for Day 2.5. The cold front will be a fast-mover and
spread snow southward all the way through the CO Rockies Friday as
snow levels fall to near 5000ft. Day 3 WPC probabilities for 6"+
are moderate over the southern WY ranges and the north-central CO
Rockies.


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


Jackson