Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
351 AM EDT Thu Jul 20 2023

Valid 12Z Thu Jul 20 2023 - 12Z Sat Jul 22 2023

...An active Thursday featuring severe storms capable of causing flash
flooding in the Central Plains, Mid-South, Great Lakes, and Northeast...

...Lengthy & dangerous heat wave to continue across the Southern Tier & in
the West...

...Cooler and more comfortable air-mass to engulf the Great Plains and
Midwest...

A strong cold front pressing south and east through the Nation's Heartland
will collide with an exceptionally hot and muggy air-mass to produce
widespread thunderstorms today and into Thursday night. The region most
at-risk for severe storms and Excessive Rainfall is the central High
Plains. The Weather Prediction Center (WPC) has a Moderate Risk (threat
level 3/4) for Excessive Rainfall, while the Storm Prediction Center has
an Enhanced Risk (threat level 3/5) for severe weather. Robust
thunderstorm activity could produce any combination of damaging winds,
large hail, tornadoes, and flash flooding there. The severe weather and
flash flood threat is also present for many locations farther east. WPC
has a Slight Risk in place that stretches from southern Kansas and
northern Oklahoma all the way to the Tennessee Valley and southern
Appalachians. There is also a Slight Risk in place over portions of the
northern Mid-Atlantic and in northeast Ohio. SPC also have an expansive
Slight Risk areas east of the Mississippi River that encompasses the
eastern Great Lakes, the Ohio Valley, and parts of the Southeast.

By Friday the cold front continues to advance farther south and east,
placing the best threat for strong-to-severe storms over the Mid-South and
Northeast. WPC has issued a pair of Slight Risks in these areas given the
potential for Excessive Rainfall rates in locations that feature overly
saturated soils. In addition, the front will set up over eastern New
Mexico, where a combination of slower moving storms and heavy rainfall has
led to a Slight Risk of Excessive Rainfall being issued there. SPC has
several Marginal Risk areas for severe weather that include southern
Arizona, northeast New Mexico, portions of the central High Plains, from
Arkansas to the Southeast coast, and in the Mid-Atlantic. By Saturday
morning, much of the Mid-South and Northeast will trend drier as the cold
front exits off the East Coast. However, the front becomes stationary over
the Gulf Coast states, setting up a stormy Saturday in the South.

For the remainder of the work-week, much of the southern tier and western
third of the U.S. will remain mired in this prolonged and dangerous heat
wave. Record breaking daytime highs and warm morning lows will be common
from the Desert Southwest and South Texas all the way east to Florida. The
forecast calls for daytime highs to soar into the triple digits in the
Desert Southwest and Southern Plains, while the Gulf Coast and Mid-South
can expect daytime highs in the upper 90s that coincide with oppressively
high dew points through Friday, resulting in sweltering heat indices as
high as 120 degrees in some spots. Meanwhile, daily low temperatures
remain quite warm with breaking record warm daily minimums expected, which
will limit relief from the heat overnight. Florida will also contend with
stifling heat thanks in large part to well above normal sea surface
temperatures and lighter than normal winds across the Sunshine State.
Please visit heat.gov, as well as the Key Messages issued by the Weather
Prediction Center and Climate Prediction Center for more information on
impacts from the heat wave.

While the cold front traversing the country is responsible in large part
for the severe weather and heavy rainfall the next couple days, it also
brings cooler temperatures and more comfortable humidity levels to the
northern Plains and Midwest. By Friday, parts of the Central Plains could
see daytime highs that are as low as 15-20 degrees below normal. This
welcomed reprieve from the heat across parts of the South will arrive by
Saturday, including in the Mid-Atlantic and Northeast where daytime highs
look to be several degrees below normal and humidity levels that are more
refreshing for mid-late July. In contrast, the heat wave will be anchored
along and west of the Rockies late Friday and into Saturday where more
record breaking heat is forecast.

Mullinax


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