FOUS11 KWBC 080840
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
340 AM EST Sat Mar 8 2025

Valid 12Z Sat Mar 08 2025 - 12Z Tue Mar 11 2025

...Southern Rockies through Oklahoma/Texas Panhandles into western
Oklahoma... Day 1...

Closed low over AZ/NM border will slowly fill as it shifts east to
northwest TX today and along the Red River tonight. A strong SWly
jet streak persists over west TX today, aiding ascent as the
associated surface trough shifts east. This deep layer lift and
increasing moisture will result in expanding precip over N Texas
and OK through this afternoon with an axis of moderate to heavy
precipitation across the TX Panhandle through central OK. Height
falls under the upper low and dynamic cooling in the banding should
allow snow to fall/accumulate over the TX Panhandle into western
OK this afternoon. 00Z HREF mean snow rates are generally not that
high, up to 0.75"/hr, though diurnal effects are probably causing
some of the limitation. Generally speaking, if snow bands become
strong/heavy enough they can overcome diurnal effects and
accumulate. Day 1 PWPF for >4" is 40-60% across the central TX
Panhandle, particularly along the I-40 corridor. Some probabilities
for >2" extend east into OK, but really it comes down to the
banding. The NAMnest likely remains too heavy/snowy, but the recent
HRRRs have trended a bit colder/snowier and a blend of these two
models is probably a decent approach.


...Washington to northwest Montana...
Days 2-3...

A deepening trough from low pressure over the Gulf of Alaska will
interact with a building ridge across the Desert Southwest to
funnel strengthening S/SW flow into western WA tonight, expanding
east to the northern Rockies through Monday. A weak shortwave and
accompanying vorticity lobe will swing onshore Sunday evening, and
along with the right entrance of a jet streak over Canada, enhance
lift. This will result in increasing wintry precipitation over the
WA Cascades and Olympics, pivoting into the Northern Rockies Sunday
night. Snow levels on the WA Cascades will generally be around
4000 ft during the heaviest precipitation, but will crash to as low
as 1500 ft just before precip ends Monday morning. This combined
with the transient nature of forcing suggests most of the impactful
snow will remain above pass levels, but Day 2 WPC probabilities
for >6" are 70-90% in the WA Cascades, with Day 2.5 probs 30-60%
for the Lewis Range in Glacier NP.


The probability of significant icing is less than 10 percent.


Jackson


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