Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
410 PM EDT Thu Sep 17 2026

Valid 00Z Fri Sep 18 2026 - 00Z Sun Sep 20 2026

...Heavy rain and flash flooding threats shifting from the southern
Rockies tonight to across the north-central U.S. over the next couple of
days...

...Record-challenging high temperatures continue across the South-Central
U.S....

After a very active day of flash flooding across the Southwest and Great
Basin, the focus for heavy rainfall will shift toward the southern Rockies
this evening, and across the northern Plains to the lower Great Lakes
during the next couple of days. This is in response to a relatively deep
and slow-moving upper low moving through the Intermountain West toward the
Great Plains, spawning low-pressure waves along a meandering front. WPC
maintains a slight risk of excessive rainfall for the southern Rockies
through this evening due to additional thunderstorm development in the
moisture-laden air mass. Meanwhile, a slight risk of excessive rainfall is
forecast to emerge across the northern Plains through tonight. By Friday,
the focus of excessive rainfall will shift eastward across the upper
Midwest, reaching the lower Great Lakes on Saturday. For the East Coast,
more widely scattered showers and embedded thunderstorms can be expected
from New England to the Mid-Atlantic through tonight, shifting farther
south into the southern Mid-Atlantic Friday into Saturday. This is in
response to a Canadian high-pressure system pushing the front farther
south into the eastern U.S. over the next couple of days.

As we head deeper into September, cooler air from Canada is beginning to
dip further into the Northern Tier states, bringing cooler-than-normal
temperatures behind the aforementioned low-pressure waves. Meanwhile, an
upper-level high associated with the persistent heat dome remains strong
across the South, resulting in a pronounced north-south temperature
contrast. High temperatures in the 60s to lower 70s can be expected north
of the meandering front across the northern tier states, compared to upper
90s and triple-digit highs south of the front across the Southern Plains
and Mid/Lower Mississippi Valley. High temperatures reaching the upper 90s
to lower 100s will challenge daily records from the Southern Plains to the
lower Mississippi Valley where Heat Advisories remain in effect. By this
weekend, the stronger push of cool Canadian air will begin to show signs
of breaking down the stubborn upper high. Meanwhile, remnant instability
associated with a stationary front on the southern edge of the heat dome
will continue to bring scattered thunderstorms with some tropical heavy
downpours across the southern half of the Sunshine State. A marginal risk
of excessive rainfall is now in place across southern Florida including
the Keys through Saturday.


Kong/Asherman


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

--- MBSE BBS v1.1.7.2 (Linux-x86_64)
 * Origin: Outpost BBS * Johnson City, TN (618:618/1)