423
FXUS01 KWBC 170804
PMDSPD

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
359 AM EDT Mon Aug 17 2026

Valid 12Z Mon Aug 17 2026 - 12Z Wed Aug 19 2026

...Severe thunderstorm, heavy rainfall, and flash flooding threats
from the Midwest to the Mid-Atlantic today, then across the
north-central U.S. on Tuesday...

...Dangerous heat persists in the South and Southeast, while
building into the Southwest early this week...

As an upper-level high pressure system continues to sustain the
heatwave across the South and Southeast, a cool air mass from
Canada is forecast to gradually dip into the northern tier states
over the next couple of days. The repeated rounds of heavy rain
and thunderstorms from the Midwest to Mid-Atlantic will continue
for one more day today before a cold front finally sweeps the
unsettled weather off the East Coast on Tuesday.  In the meantime,
the best chance of heavy rain and thunderstorms is expected today
across the upper Ohio Valley to the central Appalachians, with
thunderstorms possibly turning severe later today across eastern
Tennessee to western North Carolina.  By Tuesday, slightly cooler
and drier air behind the cold front will allow only scattered
showers to develop along the central to southern Appalachians.
Meanwhile, showers and some embedded thunderstorms are expected
across interior New England as a low pressure wave develops over
the Gulf of Maine before sliding off into the Canadian Maritimes
Wednesday morning, ending the showers across New England.

On Tuesday, the next cold front dropping southward into the
Northern Plains from Canada will help spark clusters of strong to
severe thunderstorms across the north-central U.S.  A Slight Risk
(level 2/5) area of severe weather is anticipated for this area
along with a slight risk of flash flooding. From Tuesday night
into Wednesday morning, the cold front will begin pushing the
heavy rain and severe weather threats farther east across the
Midwest and lower Great Lakes.  Much cooler air behind the front
will drop temperatures into the 40s closer to the Canadian border
in the upper Midwest by Wednesday morning.

As the mid-summer heatwave continues across the South and
Southeast, expect more days with high temperatures soaring into
the upper 90s and low 100s, along with heat indices up to 115
degrees. Residents are advised to follow proper heat safety tips
by limiting outdoor activity, staying hydrated, ensuring access to
A/C or cooling centers, and checking on vulnerable friends,
neighbors, and family members. Additionally, the Southwest begins
to heat up once again on Monday and Tuesday as high temperatures
begin to climb back into widespread 100s and into the 110s.
Extreme Heat Watches are in effect for much of southern NV,
northwest AZ, and southeast CA, with Extreme Heat Warnings
spanning from southern AZ to the deserts of far southeast CA.
Heat advisories are also posted for portions of southern CA.


Kong/Snell


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




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