Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
400 PM EDT Fri Jul 28 2023

Valid 00Z Sat Jul 29 2023 - 00Z Mon Jul 31 2023

...Excessive Heat Advisories and Warnings are in effect for portions of
the East Coast, Central/Southern Plains, and over the Southwest...

...Temperature relief expected for the Northeast and Mid-Atlantic as a
cold front descends into the northern tier...

...An Enhanced Risk of Severe Thunderstorms is in effect for portions of
the lower Great Lakes on Friday evening...

Widespread near-record heat continues to impact a large portion of the
U.S. today as a large upper-level ridge sits over much of the central and
eastern U.S. Heat Advisories and Warnings are in effect for the
Mid-Atlantic, Northeast, and portions of the Central Plains/Midwest. Some
cities currently under Excessive Heat Warnings include Virginia Beach,
Washington D.C., Philadelphia, St. Louis, and Kansas City. These areas may
see high temperatures climb well north of 90F, even 100F in some areas. In
addition, oppressive humidity currently affecting much of the country will
contribute to widespread heat indices of 100-110+ over these areas.
Nighttime temperatures may only fall into the upper 70s and low 80s, which
will reduce overnight relief from the daytime heat. Many places are set to
break their temperature records for daytime highs as well as warm
nighttime lows through Saturday morning. If you are affected by this heat
wave, it is imperative to practice heat safety, especially if spending
extended periods of time outdoors.

For those on the East Coast, temperature relief arrives sooner than later.
Areas of scattered thunderstorms along and preceding a cold front
approaching from Canada may help to limit the heat on Saturday for those
in the Northeast. On Sunday, this cold front will progress through
Mid-Atlantic, ultimately ending the heat wave for much of the East Coast.
However, over the Central Plains and southern tier, a more gradual relief
from the heat is expected. A surface cold front will slowly descend over
the northern tier of the country as the upper-level ridge responsible for
the hot conditions focuses over the central U.S. High temperatures over
the weekend are set to be in the mid to upper 90s over much of the central
and southern U.S., with heat index values of 100-105F. By Sunday,
temperatures over the central Plains will trend closer to average for this
time of year, and the heat wave will focus over the Southern Plains and
Gulf Coast.

A few areas of severe weather and heavy rain are expected to form during
the short-term forecast period. The Storm Prediction Center has issued an
Enhanced Risk of Severe Thunderstorms (level 3/5) over the lower Great
Lakes region, effective through Saturday morning. Upper-level energy over
the northern Plains is expected to interact with an extremely unstable air
mass centered over Iowa, which will help to create an area of strong
thunderstorms on Friday evening. The main threats expected from this area
of thunderstorms are damaging wind gusts and large hail. Additionally, WPC
has issued a Slight Risk of Excessive Rainfall (level 2/4) for this
system, noting the potential for repeated rounds of thunderstorms with
intense rainfall rates, creating localized flash flooding concerns. On
Saturday, this area of thunderstorms is expected to continue into the
Mid-Atlantic. Widely-scattered thunderstorms are expected to develop over
the Mid-Atlantic into southern New England ahead of the cold front. The
Storm Prediction Center has issued a Slight Risk for Severe Thunderstorms
(level 2/5) over this area, with damaging winds being the primary severe
threat.

Over the Southeast, a tropical upper-low  and associated surface system
continues to force a wide region of scattered thunderstorms over the
region. The surface low is expected to progress northward through
southeastern Georgia before eventually weakening over the weekend.
Persistent onshore flow may result in locally heavy rainfall amounts along
the southeast coasts of Georgia and South Carolina on Friday evening. Over
the Southwest, summer heat will continue, with portions of the Southwest
and southern California set to experience near record highs and warm
nighttime lows. An gradual influx of upper-level moisture will begin to
impact the region, which may result in an increase in thunderstorm
coverage over the course of the weekend.


Genz


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