Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
449 AM EDT Mon Oct 26 2020

Valid 12Z Mon Oct 26 2020 - 12Z Thu Oct 29 2020


...Southern Rockies/Plains...

As an upper low closes off over the Southwest, heavy snows are
expected to continue moving south into the southern Rockies, while
a wintry mix develops out over the Plains, with significant ice
accumulations possible across portions Texas and Oklahoma.

As a deep, positively-tilted upper trough continues to settle
south, models show an upper low closing off early in the period
near the Four Corners region.  Strong lift and ample moisture,
interacting with very cold air spilling south, will support heavy
snows continuing Monday morning across the San Juan and Sangre de
Cristo mountains, before shifting farther south into the central
New Mexico ranges later in the day.  WPC PWPF shows high
probabilities for additional snow accumulations of a foot or more
across portions of the San Juan, Sangre de Cristo, Jemez and
Sandia Manzano mountains. Meanwhile farther to the east, surface
to low level northeasterly flow and southwesterly flow aloft will
set the stage for a wintry mix from western and central Texas,
through western and central Oklahoma, and into eastern Kansas and
Missouri.  Right-entrance region upper jet forcing, in addition to
low-to-mid level frontogenesis, are expected to support a period
of heavier precipitation across the region early Monday, raising
the potential for significant ice accumulations from the Texas
Hill Country northward to central Oklahoma.  WPC guidance reflects
the overnight model trend, led by the hi-res guidance, toward a
colder solution across this region. 

Following a period of scattered, light precipitation late Monday,
organized heavier precipitation is expected to return portions of
the southern Plains early Tuesday.  As the upper low begins to
turn east, increasing lift and a surge of deeper moisture are
expected to once again raise the potential for higher
precipitation rates across portions of western and central Texas
into Oklahoma, with another round of significant ice accumulations
possible from the Texas Hill Country northward into central
Oklahoma.  The heaviest storm total ice accumulations are expected
to center across southwest into central Oklahoma, where WPC PWPF
shows high probabilities for ice accumulations exceeding a
quarter-inch.  Meanwhile within the deeper cold air, periods of
heavier snow are expected across the Texas Panhandle and eastern
New Mexico.

As the upper low moves east of the southern Rockies on Wednesday,
southerly winds ahead of a developing low level circulation will
end the potential for additional snow/ice accumulations across
central Texas and Oklahoma.  However, cold air on the backside of
the system should be sufficient for additional light snow and ice
accumulations continuing through early Wednesday across the
Panhandle region and northeastern New Mexico, before lifting
farther north into eastern Colorado and western Kansas late in the
period.

Pereira