Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
352 PM EDT Tue Sep 20 2022

Valid 00Z Wed Sep 21 2022 - 00Z Fri Sep 23 2022

...Scattered to numerous flash floods likely through at least Thursday
across parts of the Southwest, central Great Basin, and central Rockies...

...Severe thunderstorms possible from northern Utah to southern Idaho and
over the Lower Great Lakes on Wednesday...

...Record breaking heat to become less widespread throughout the
south-central United States on Wednesday and confine to the Deep South on
Thursday...


An active weather pattern is forecast to continue impacting much of the
Great Basin, Rockies, and Southwest over next few days. The atmospheric
setup expected to produce numerous showers and thunderstorms over the
region includes a potent upper-level low pushing into northern California
on Wednesday and a robust surge of tropical moisture extending from the
eastern Pacific Ocean to the Four Corners Region. As a result,
thunderstorms capable of containing intense rainfall rates could lead to
scattered flash floods through tonight over parts of Arizona, New Mexico,
the Four Corners and immediate surrounding areas. By Wednesday,
atmospheric moisture content is expected to become quite anomalous and
centered over the Four Corners. This will lead to the potential for
numerous instances of flash flooding, which has prompted a Moderate Risk
(level 3/4) of Excessive Rainfall to be issued over northwest New Mexico,
western Colorado, eastern Utah, and northern Arizona. Lingering rainfall
chances will exist on Thursday as the upper-level low moves farther north
into the northern Plains. Total rainfall amounts around 1 to 3 inches are
forecast throughout southwest Colorado and the Four Corners, with
localized amounts near 4 inches possible. Heavy rainfall is also possible
farther north into the northern Rockies and closer to the aforementioned
upper-level low. Isolated to scattered flash floods, as well as the
potential for severe thunderstorms will be the main concerns on Wednesday.
SPC has issued a Slight Risk (level 2/5) of severe weather from northern
Utah to south-central Idaho, with damaging winds gusts anticipated to be
the main hazard.

An advancing cold front may lead to a few severe thunderstorms over
northern Wisconsin this evening before the threat shifts into the Lower
Great Lakes on Wednesday. SPC has issued a Slight Risk of severe
thunderstorms from the Tug Hill Plateau of New York to central Ohio, where
the potential exists for damaging wind gusts, large hail, and isolated
tornadoes. The severe weather threat will continue to shift south and east
along the cold front on Thursday toward the Mid-Atlantic States.
Elsewhere, rain will put a damper on outdoor fall activities throughout
the central Plains on Wednesday and Thursday. Rain could be heavy at times
along the Nebraska-Kansas border.

The other major weather story for the Nation through midweek will include
the rather large area of above normal and record breaking temperatures
stretching over the south-central and southeastern United States. For
many, the good news is that the upper-level ridge responsible for these
summer-like temperatures will gradually weaken by the end of the week and
the previously mentioned cold front will usher in much cooler
temperatures. However, highs are still forecast to soar into the 90s from
the Ohio Valley to the southern Plains on Wednesday, with triple digits
possible in the southern Plains and lower Mississippi Valley. By Thursday,
the above normal temperatures region will shrink toward the Deep South,
but highs will remain relatively uncomfortable and into the upper 90s from
Texas to the Carolinas. Dozens of daily high temperature records could be
set over the aforementioned regions by the end of the week. Conversely,
low temperatures are expected to dip below normal and into the 30s and 40s
throughout the northern Plains over the next few days while underneath a
modest surface high pressure system.

Snell


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