Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
406 PM EDT Tue Oct 12 2021

Valid 00Z Wed Oct 13 2021 - 00Z Fri Oct 15 2021

...First winter storm of the season to bring heavy snow to the
Northern/Central Rockies today and the northern High Plains overnight...

...Severe weather and heavy rain will persist in the Central and Southern
Plains through Thursday...

...Mild temperatures continue throughout the eastern US while frigid highs
and sub-freezing lows are expected out West...

A deep low pressure/frontal system moving through the Central Rockies and
into the Northern Plains will serve as the focus for active weather of all
types through the short-range period, including the first winter storm of
the season. With favorable dynamics and high atmospheric moisture
accompanying this ongoing system, heavy snowfall with additional
accumulations up to and in excess of 12" are expected in the Northern
Rockies and High Plains as well as areas of high elevation in the Central
Rockies. Winter Storm Warnings and Winter Weather Advisories will remain
in effect until late this evening for the Central and Northern Rockies,
while locations farther east in the High Plains will hold on to these
warnings and advisories until midday tomorrow. Strong winds with gusts up
to 60 mph are also expected to accompany this storm as it moves through
the Rockies and into the Central High Plains. High Wind Warnings are
currently in effect for the Central/Southern Rockies and Central High
Plains as these winds may knock down trees and power lines and blow around
already fallen snow, lowering visibility and making travel hazardous.

Ahead of the cold front on the eastern edge of this system warmer
temperatures, surface instability, and high atmospheric moisture
throughout the Central and Southern Plains will support the development of
showers and thunderstorms capable of becoming severe. Numerous supercells
are expected to form throughout the day that will have the potential to
produce damaging winds, large hail, and multiple tornadoes. The Storm
Prediction Center has issued a Moderate Risk of Severe Thunderstorms for
western Kansas, western Oklahoma, and the northeastern Texas panhandle as
these areas hold the greatest probability of receiving hail 2+" in
diameter and significant tornadoes through tomorrow morning. While the
severe weather threat tapers off on Wednesday, the potential for
widespread flash flooding ramps up as heavy rain focused around the
trailing cold front inundates portions of the Southern Plains. With strong
deep-layer ascent in place and atmospheric moisture levels well above
normal, a swath of 3-6+" rainfall accumulations is expected across central
Texas. These high accumulations combined with the potential for hourly
rainfall rates of 2-3" in some areas has prompted the Weather Prediction
Center to issue a Moderate Risk of Excessive Rainfall for portions of
central Texas from Wednesday morning through Thursday morning. Heavy
rainfall will continue in central Texas on Thursday as moisture from
Hurricane Pamela is transported northeast and interacts with the
quasi-stationary boundary draped through the state, thereby prolonging the
risk of flash flooding through Friday.

Throughout the short-range period a strong temperature contrast will exist
across the country. High pressure locked in place over the eastern
seaboard will allow moderately above normal temperatures to persist across
the eastern US, while the storm system out west will advect cool air south
from higher latitudes, dropping daily highs 20 to 30 degrees below average
into the 30s and 40s. Freeze Watches and Warnings are currently in effect
over portions of the Southwest and Central Great Basin.

Zavadoff


Graphics are available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php