Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
343 PM EDT Tue Aug 22 2023

Valid 00Z Wed Aug 23 2023 - 00Z Fri Aug 25 2023

...Extremely dangerous heat will persist across a widespread region
spanning from the Central to Southeast U.S. this week...

...Heavy rain and gusty winds associated with Tropical Storm Harold
continue over South Texas today...

...Scattered flash flooding concerns exist across parts of the Great Basin
and Southwest...

A searing August heat wave is set to continue this week underneath a
potent, potentially record breaking upper-level ridge anchored over the
Mid-Mississippi Valley, which will drive oppressive heat from the Central
to Southeast U.S. High temperatures throughout these areas are forecast to
reach into the upper 90s and low 100s each day through the end of the work
week. 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 over the next few days. 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 17 states and roughly 150
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 Storm Harold continues to churn inland across South
Texas, where current radar and surface observations show banded heavy
rainfall and gusty winds wrapping around the circulation. A few Flash
Flood Warnings are noted around Corpus Christi where high rainfall rates
are driving flash floods in urbanized and coastal areas. A threat of
scattered flash and urban flooding will continue through early tomorrow
over South Texas as Harold tracks into northern Mexico. Tropical storm
force winds and perhaps a tornado or two are also expected to threaten
South Texas for the next several hours as Harold moves inland. By tomorrow
and Thursday, the mid-level remnants of Harold and its moisture is
forecast to push toward the Southwest and Southern Rockies. This may lead
to additional flash flooding concerns, especially near the more
flood-prone slot canyons in Utah on Thursday where a Slight Risk (level
2/4) is in effect on Thursday.

Across the Northern Great Basin and Intermountain West today, scattered
flash flooding is possible as anomalous moisture content and uniform
southerly flow supports potentially training showers/thunderstorms.
Looking farther east, precipiation chances continue to circumvent the
strong upper high over the Midwest and progress from the Great Lakes today
to the Northeast/Central Appalachians by Wednesday and Thursday. Some of
the strongest thunderstorms could yield isolated instances of flash
flooding, damaging wind gusts, and severe hail. The West and Northeast
will enjoy below average temperatures to go along with the rain chances
and clouds, as highs for most locations remain in the 70s and low 80s.

Asherman/Snell


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