Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
331 AM EDT Mon Sep 27 2021

Valid 12Z Mon Sep 27 2021 - 12Z Wed Sep 29 2021

...Isolated chances for flash flooding found across parts of the Southwest
and Four Corners region through Wednesday morning...

...Cold front to bring unsettled weather and cooler temperatures for the
Northwest today and Northern Rockies by Tuesday...

...Well above average and potentially record-breaking warmth found
throughout the central/northern Plains and Midwest...

An upper-level low pressure system advancing across the Southwest will
help produce a few more rounds of scattered showers and thunderstorms as
the monsoon season draws to a close. Given the sufficient moisture in
place, intense rainfall rates will be possible and could create isolated
instances of flash flooding. A Marginal Risk (level 1/4) of excessive
rainfall has been issued for parts of central Arizona and western New
Mexico, as well as the Four Corners region through Wednesday morning.
Farther north, a potent cold front in tandem with a deep upper-level
trough is currently approaching the Pacific Northwest and is expected to
swing into the northern Great Basin by this evening. Widespread showers
and much cooler temperatures will be found behind the cold front. In fact,
high elevation snow will be possible on Tuesday across the Northern
Rockies as the system advances eastward. Another potential hazard to
contend with across the western U.S. over the next couple of days is the
threat of critical fire weather. Gusty winds combined with low relative
humidity and dry fuels may produce conditions ripe for wildfires to spread
uncontrollably throughout northern Nevada in particular.

For the central U.S., autumn is nowhere to be found as high temperatures
rise into potentially record-breaking territory today and Tuesday. A
strong upper-level ridge and persistent southerly flow will allow for
temperatures to rise into the 90s throughout much of the Great Plains and
parts of the Midwest. These warm temperatures are likely to extend as far
north as the Dakotas, where temperatures are forecast to reach 20 to 30
degrees above average. A dozen or so daily high temperature records could
fall, mostly found across the northern and central Plains. Elevated to
critical fire weather is also a concern for sections of the northern High
Plains on Tuesday as southerly winds increase in intensity.

Elsewhere, a cold front dropping south across the Northeast and Ohio
Valley today could spark a few severe thunderstorms. By Tuesday, this
frontal boundary and isolated severe weather threat will shift into the
Mid-Atlantic. Gusty winds and large hail are expected to be the primary
potential weather hazard. Showers and thunderstorms are also expected to
increase in coverage across the western Gulf Coast and Southern Plains
early this week. A few severe storms are not out of the question on
Tuesday as thunderstorms develop along a dryline situated between the
Oklahoma Panhandle and West Texas.

Snell


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