Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
405 AM EDT Fri Oct 22 2021

Valid 12Z Fri Oct 22 2021 - 12Z Sun Oct 24 2021

...A trio of Pacific storm systems to produce copious amounts of rain and
mountain snow in the Northwest and California this weekend...

...Severe storms possible in parts of the Southeast; Moderate to heavy
rain and severe thunderstorms expected in the Central Plains Saturday in
association with a developing low pressure system...

...Above normal temperatures persist in the Central and Southern Plains;
more seasonal temperatures to return to the Intermountain West and
Northeast; cooler than average in the Midwest and along the West Coast...

The first in a barrage of Pacific cyclones is making for a wet, dreary,
and in some cases gusty start to the day in the Pacific Northwest. Some
locations containing burn scarred areas, however, do remain susceptible to
potential flash flooding, rapid runoff, and debris flows. A Marginal Risk
for Excessive Rainfall remains in place for burn scarred areas of the
northern Sierra Nevada today. The storm weakens as it tracks further
inland today and reaches the northern Rockies tonight. This allows for
areas of valley rain and mountain snow to transpire with light
accumulations. Precipitation remains a welcome sight for the drought
stricken areas of the Intermountain West and West Coast, and a second
storm system will usher in more beneficial rainfall to the Pacific
Northwest on Saturday. Similar to today's storm, rainfall rates could be
excessive at times and burn scarred areas could contend with rapid runoff
and debris flows. This has led to the issuance of another Marginal Risk
for those at-risk areas of Northern California and southwest Oregon on
Saturday. By Saturday night, a rapidly intensifying Pacific cyclone
directing a powerful atmospheric river squarely at the West Coast delivers
a fire hose of rich subtropical moisture into California. Snow levels will
be low enough to blanket the Sierra Nevada in heavy snow on Sunday while
prolonged periods of rain soak the coast and valleys of northern and
central California. This impressive atmospheric river will result in
heavier rainfall amounts and in a shorter time span, leading to more flash
flooding and debris flow concerns for burn scarred areas of California. In
response, a Slight Risk has been issued for much of Northern California on
Sunday.

Further east, a cold front draped along the East Coast may trigger
additional thunderstorms in parts of the Southeast today. Some
thunderstorms could be severe, especially in eastern North Carolina. Heavy
showers and strong thunderstorms are also possible out ahead of the front
in South Florida. Meanwhile, an organizing area of low pressure in the
Southern Plains will become a focus for strong-to-severe thunderstorms
overnight. By Saturday, an upper level impulse exiting the Rockies
provides a boost in the development of the Southern Plains frontal system
and in doing so, generating a larger swath of showers and thunderstorms in
the Middle Mississippi Valley. The setup is favorable enough for severe
weather that the Storm Prediction Center has issues a Slight Risk on
Saturday for northeast Kansas. By Sunday morning, widespread showers and
thunderstorms will extend from the central Plains to the Lower Great
Lakes.

Temperature regimes will be clearly depicted thanks to a pair of frontal
systems east of the Rockies. Temperatures north of a quasi-stationary
boundary draped from the northern High Plains to the Ohio Valley may feel
more like early November with departures averaging nearly 10 degrees below
normal both Friday and Saturday in the Midwest. A cold frontal passage in
the Northeast and Ohio Valley prompts the return of seasonally cool
conditions for these regions. To the South, temperatures are considerably
warmer with the warmest anomalies focused in the southern High Plains.
Much of the High Plains can expect temps in the 70s but Saturday's highs
will eclipse 90 degrees along the Rio Grande in South Texas and widespread
80s in Texas and Oklahoma. The combination of dry and hot conditions as
well as increasingly gusty winds promotes favorable fire weather
conditions Saturday, and thus an Elevated Risk has been issued in the
SPC's Fire Weather Outlook. Along the West Coast, the persistent onshore
flow and unsettled weather pattern looks to keep temperatures below normal
to close out the week and throughout the weekend. Daily high temperature
anomalies are likely to range between 10 and 20 degrees below normal
across much of California. 

Mullinax

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