Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
348 AM EST Wed Nov 23 2022

Valid 12Z Wed Nov 23 2022 - 12Z Sat Nov 26 2022

...Northern to Central Rockies...
Day 1...

A northern stream shortwave trough currently over central ID will
continue to dive southeast down the rest of the Rockies through
this evening. Upper dynamics ahead of the trough axis as well as
difluent flow from being in the left exit of the strong NNWly jet
will provide enough lift along with Pacific moisture streaming
over the ridge that extends up BC to allow moderate to locally
heavy snow today in MT/WY/northern CO terrain. Snow levels will be
at or below ground level with orographic lift focusing most of the
notable QPF over terrain. Day 1 WPC probabilities for 6 or more
inches are moderately high for ranges from central MT to northern
CO including the Bighorn and Medicine Bow of WY.


...Texas Panhandle to Southeast New Mexico...
Days 2/3...

The amplifying shortwave trough digging down the Rockies will
close later tonight over CO before slowing as it drifts south over
NM through Thursday, and likely stalling over west TX into or
through Friday as it becomes cutoff before ejecting east. Coupled
jet streaks are expected to intensify both upstream and downstream
of this low, resulting in a period of impressive deep layer
ascent. 00Z guidance came into better agreement compared to prior
suites. Confidence continues to increase that intense UVVs driven
by low to mid level frontogenesis and deformation N/NW of the low,
and aided by steepening lapse rates near the cold core aloft,
which will produce enough dynamic cooling for moderate to heavy
snow accumulations on the High Plains of NM through the Panhandle
of TX and possibly into western OK. The slow/stalling movement of
the low will prolong the snow threat which looks to start Thursday
afternoon. Low-level thermals will be modest, but sufficient lift
of the warm conveyor belt into a TROWAL is expected to produce
locally heavy bands of snow that should overcome marginal thermals
and accumulate. Day 2 snow probabilities are moderately high for 4
or more inches over the north-central IX/NM border (near I-40)
which expand south through the rest of the TX Panhandle into
southeast NM as well as for the northern Sacramento Mtns.


Jackson