129
FXUS01 KWBC 190817
PMDSPD

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
400 AM EDT Wed Aug 19 2026

Valid 12Z Wed Aug 19 2026 - 12Z Fri Aug 21 2026

...Heavy rain and flash flooding threats across the Midwest, Ohio
Valley and southern Arizona today, shifting east to the
Mid-Atlantic coast on Thursday...

...Severe storms possible across mid-Mississippi Valley today
through tonight...

...Dangerous heat persists in the South while building into the
Southwest...

A cool air mass arriving from southern Canada will push a cold
front across the northern tier states over the next couple of
days.  The focus of heavy rain and severe thunderstorm potential
will be near the northern boundary of a persistent heatwave across
the southern U.S. Clusters of organized heavy showers and
thunderstorms will continue traveling eastward across the central
Plains toward the mid-Mississippi Valley this morning. These
heavy rain and thunderstorms are forecast to become more focused
in the vicinity of the mid-Mississippi Valley later today through
tonight ahead of a low pressure wave traveling eastward along a
meandering front as the cold front from Canada dips southward
toward the Midwest.  SPC has a slight risk of severe thunderstorms
across the mid-Mississippi Valley today while WPC has a slight
risk of excessive rainfall extending farther north into the
Midwest and Ohio Valley.

By Thursday, the cold front from Canada will advance farther east
and begin to merge with the meandering front to the south.  A
convergence zone sandwiched between this pair of fronts will focus
a corridor of enhanced rainfall.  Heavy rain with embedded
thunderstorms is possible along this corridor roughly from I-95
east to the northern Mid-Atlantic coast.  WPC has highlighted this
area for a slight risk of excessive rainfall mainly later on
Thursday when daytime heating is maximized.  By Thursday night
into early Friday, the heavy rain should temporarily exit the
Mid-Atlantic coast as a low-pressure wave slides off the coast of
southern New England.

Meanwhile, monsoonal showers and thunderstorms will be most active
during the late-day hours across the Four Corners states, where
the WPC has highlighted a marginal risk of Excessive Rainfall
through the next couple of days. In addition, a slight risk is in
place across southern Arizona for today.

Temperature-wise, the southern tier of the Lower 48 remains mired
in a steamy air-mass even by mid-to-late August standards. Record
highs and record warm minimum temperatures will be common with the
Southeast at the heart of the anomalous heat through today. The
upper ridge is forecast to strengthen over the Southwest while
cool Canadian air dips further into the Great Lakes. Some cases of
record-breaking warmth are expected in the Desert Southwest and
Southern Plains as temperatures dip into the 40s near the Canadian
border in the upper Midwest. Extreme Heat Warnings are in effect
for much of the Desert Southwest, and Extreme Heat Warnings remain
in effect across portions of the southern Plains to the Deep
South.  Heat Advisories are in effect for all of Florida and the
southeast U.S. coast.  Overnight lows will be so warm (low 80s in
some cases) that, when combined with oppressive dew points,
little-to-no relief from the scorching daytime highs will be
available. 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.

Kong


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




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