Message 28312 in WX.USA
From: KF5JRV
Date: Thu, 20 Aug 26 09:21:00 Z
Newsgroups: WX.USA
Subject: NWS USA WX Forecast - Aug 20
Message-ID: <30063_KF5JRV>
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Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
400 AM EDT Thu Aug 20 2026
Valid 12Z Thu Aug 20 2026 - 12Z Sat Aug 22 2026
..Heavy rain, flash flooding, and severe weather threats
spreading from the Ohio/Tennessee Valley this morning to the
Mid-Atlantic coast later today...
..Severe thunderstorms possible across the upper Midwest to the
central Plains today, mainly over the north-central Plains on
Friday...
..Dangerous heat persists in the South while building into the
Southwest...
As a cool air mass from Canada advances toward the northeastern
U.S. against a persistent and stagnant heat dome anchored across
the southern tier states over the next couple of days, the focus
of heavy rain, flash flooding, and severe weather and
thunderstorms will shift from the Ohio/Tennessee Valley this
morning to the Mid-Atlantic coast later today. A convergence zone
sandwiched between the stationary front to the south and the cold
front from Canada will focus a corridor of enhanced rainfall.
Heavy rain with embedded thunderstorms is expected 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 today when daytime heating is
maximized. In addition, SPC has highlighted a slight risk for
severe weather where the main threat is damaging wind gusts. By
tonight 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. Some lighter rainfall may wrap around
the low pressure wave toward southern New England on Friday.
Day-time heating is forecast to trigger the next round of heavy
thunderstorms later on Friday across the Carolinas to the
Mid-Atlantic where a slight risk of excessive rainfall is
highlighted. From Friday night into Saturday morning, showers and
embedded thunderstorms are expected to advance up the Mid-Atlantic
states as a trough of low pressure deepens over the Great Lakes.
Over the midsection of the country, another round of severe
weather is possible for eastern Nebraska into Minnesota and
Wisconsin this afternoon into the evening ahead of a front
trailing from a low pressure wave moving across Minnesota into the
U.P. Michigan. SPC has outlined a slight risk of severe weather
for the area where the main threat will be large hail, and
isolated wind damage.
On Friday, much of central and eastern Nebraska will yet again
experience another round of severe weather as the trailing front
pushes against the northern boundary of the heatwave across the
South where ample moisture, strong instability and shear are in
place to initiate some super cell thunderstorms. SPC has
highlighted a slight risk for severe weather where the main threat
will be isolated to scattered damaging hail (some greater than 2
inches) and some severe wind gusts for Friday afternoon into the
evening hours. As for the Southeast, scattered to numerous
thunderstorms are forecast within a very moist and unstable
environment along a surface trough. Single to multi-cell
convection will pose the risk for excessive rainfall where WPC has
highlighted a slight risk for excessive rainfall from northern
portions of South Carolina to the southern portions of Virginia.
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 where showers
will become more widespread heading into the weekend. 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/Green
Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php
73 de Scott KF5JRV
Pmail: KF5JRV@KF5JRV.#NWAR.AR.USA.NA
Email KF5JRV@gmail.com
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