Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
415 PM EST Sun Jan 10 2021

Valid 00Z Mon Jan 11 2021 - 00Z Thu Jan 14 2021


Day 1...
...Eastern Texas through the Lower Mississippi Valley...
With some change in the details, there still remains a good model
signal for an axis of significant snows setting up across portions
of eastern Texas and the lower Mississippi valley Sunday evening
into the overnight. 

An upper low currently centered over Northwest Texas will continue
to move east across North Texas and into the ArkLaTex this
evening.  While consensus of the models has shifted a little
farther to the south, they continue to show a southwest-northeast
oriented low level center/frontal zonal promoting an axis of
heavier precipitation and in-turn a greater threat for significant
snow accumulations centered from Deep East Texas across northern
Louisiana into central Mississippi this evening and overnight. 
Latest WPC PWPF indicates that widespread accumulations of 1-2
inches are likely, with locally heavier amounts possible across
this region.  Expect the potential for heavy snow to quickly
decrease on Monday as the system begins to the shear out to the
east into the Tennessee valley.

Days 2-3...
...Pacific Northwest and Northern Rockies...
An atmospheric river event is set to unfold, with heavy
precipitation likely to develop across across western Washington
and Oregon beginning Monday night and continuing through Tuesday
into early Wednesday.   High snow levels are expected to confine
the threat for heavy snow to the higher elevations of the Olympics
and northern Cascades -- where several feet are likely by
Wednesday evening.  Through late Tuesday there is some threat for
locally heavy snow accumulations across the higher elevations of
the northeastern Washington and northeastern Oregon mountains into
the Rockies.  However, the potential is expected to increase on
Wednesday as well-defined shortwave, drives a strong cold front
into the region.

For Days 1-3, the probability of significant icing (0.25-inch or
greater) is less than 10 percent.

Pereira