Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
425 AM EDT Sun Oct 25 2020

Valid 12Z Sun Oct 25 2020 - 12Z Wed Oct 28 2020


...Winter Storm impacting the western and central U.S....

An amplifying upper trough will continue to bring sharply colder
temperatures, along with moderate to heavy snows farther south
through the central Rockies and Plains on Sunday.  A well-defined
shortwave currently centered over the northwestern U.S. will
continue to dig south into the Great Basin on Sunday.  Increasing
lift and moisture ahead of the system, interacting with cold air
pushing south through the Plains and Rockies, will support
widespread snows across the central Rockies and Plains.  While the
heaviest totals are expected across the higher elevations of the
Colorado Rockies, where WPC PWPF is indicating widespread amounts
of a foot or more, impactful accumulations are also expected
farther east, including along the I-25 corridor.  Increasing low
level convergence/easterly flow, is expected to help support
heavier totals, with WPC PWPF continuing to show probabilities of
50 percent or greater for accumulations of 8-inches or more across
this region, including the Denver metro area.

On Monday, models show the upper wave continuing to drop farther
south, with a closed circulation beginning to develop near the
Four Corners region.  By early Monday, drier conditions can be
expected across northern Colorado.  However, snows are expected to
continue across southern Colorado while extending south into New
Mexico, with additional heavy accumulations likely across the San
Juan and Sangre de Cristo mountains.  Meanwhile, snows will also
begin to develop farther southwest across northern and central
Arizona, with significant accumulations possible along the
Mogollon Rim and White Mountains.

By early Monday, southwesterly flow aloft, moving warm moist air
over shallow cold air sliding south, will set the stage for a
wintry mix, with accumulating ice becoming likely across portions
of Northwest Texas and western to central Oklahoma.  Periods of
freezing rain are likely to continue through Tuesday into early
Wednesday across portions of western Texas and Oklahoma, while
spreading farther north into Kansas.  While confidence in the
details is limited, latest WPC PWPF shows 50 percent of higher
probabilities for ice accumulations exceeding 0.10 inch from the
eastern Texas Panhandle through much of western Oklahoma. 

Pereira