Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
352 AM EDT Wed Aug 23 2023

Valid 12Z Wed Aug 23 2023 - 12Z Fri Aug 25 2023

...Over 100 million people under heat alerts from the Midwest to the Gulf
Coast as record-breaking temperatures continue through the end of the
week...

...Scattered flash flooding threat spans across West Texas, the Southwest,
and central Great Basin over the next few days...

...Locally heavy rain and severe thunderstorms possible across the Lower
Great Lakes and Upper Ohio Valley...

A searing August heat wave is forecast to continue through at least the
end of this week underneath a potent upper-level ridge anchored over the
Mid-Mississippi Valley, which will drive oppressive heat from the central
U.S. to Gulf Coast States. High temperatures throughout these areas are
forecast to reach into the upper 90s and low 100s through Thursday before
a cold front dropping south begins to usher in cooler temperatures over
the Upper Midwest on Friday. When factoring in brutal humidity levels,
maximum heat indices could approach 120 degrees. While it is not uncommon
for August to feature dangerous heat, these temperatures are extremely
anomalous and likely to break numerous daily and potentially monthly
records. In fact, highs are forecast to reach up to 20 degrees above
average throughout Iowa and neighboring states today. Very warm overnight
temperatures only dropping into the upper 70s and low 80s will compound
the impacts associated with this potentially deadly heat wave. Heat alerts
(Excessive Heat Warnings, Watches, and Advisories) have been issued from
Minneapolis to New Orleans, which includes 22 states and roughly 130
million people. It is imperative to take the heat seriously and avoid
extended time outdoors, as temperatures and heat indices will reach levels
that would pose a health risk, and be potentially deadly to anyone without
effective cooling and/or adequate hydration. Remember, heat is the
number-one-weather-related cause of death in the United States.

Meanwhile, Tropical Depression Harold and its surrounding moisture is
currently pushing westward across far northern Mexico and is expected to
produce the potential for flash flooding from West Texas to the Southwest
today. As the showers and thunderstorms continue to circle around the
anchored upper high in the central U.S., the remnant tropical moisture is
forecast to turn north and enter this part of the country from
north-central Mexico, while also pushing into the central Great Basin on
Friday. Thunderstorms will be capable of containing intense rainfall rates
that could lead to rapid runoff and flooding concerns. To further
highlight the threat, a Slight Risk (level 2/4) of Excessive Rainfall has
been issued from West Texas to southern New Mexico today and southern Utah
on Thursday. Lingering anomalous atmospheric moisture content and an
approaching cold front will combine to produce additional scattered flash
flooding chances over parts of the central Rockies/High Plains on Friday.

Elsewhere, precipiation chances continue to circumvent the strong upper
high over the Midwest and progress from the Great Lakes to the Ohio
Valley/central Appalachians today. Some of the strongest thunderstorms
could yield isolated instances of flash flooding, damaging wind gusts, and
severe hail. Rain and thunderstorm chances will continue towards the end
of the week while also progressing eastward towards the Mid-Atlantic and
Northeast.

Snell


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