Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
306 AM EDT Thu Jul 27 2023

Valid 12Z Thu Jul 27 2023 - 12Z Sat Jul 29 2023

...Dangerous heat wave to begin in Northeast & Mid-Atlantic on Thursday
and continue through weekend...

...Severe thunderstorms and flash flooding possible throughout portions of
Northeast on Thursday...

...Record-breaking heat to continue across Southwest and Central U.S.
through end of week...

A dangerous heat wave will begin Thursday for much of the I-95 corridor as
daytime high temperatures approaching 100 F combined with oppressive
humidity will produce heat index values of 105+ F through Saturday. Major
metropolitan areas such as Washington D.C., Philadelphia, and Boston are
under a Heat Advisory, while an Excessive Heat Warning is in effect for
the New York City metro area. Numerous high maximum and high minimum
temperature records are forecast to be broken through Saturday, as
nighttime lows will be as much as 10-15 degrees above average for the
region, exacerbating the potential heat-related health impacts. It is
imperative that residents in the Northeast and Mid-Atlantic practice heat
safety this week as the hottest stretch of the summer begins on Thursday
and continues through Saturday.

In addition to the hot weather, an upper-level shortwave will help drive
the risk for severe weather throughout the Mid-Atlantic and Northeast on
Thursday, resulting in the Storm Prediction Center (SPC) highlighting an
area with a Slight Risk of Severe Thunderstorms from Washington D.C.
northward through Portland, ME. Furthermore, anomalously moist air
advecting northward ahead of the shortwave will set the stage for possible
flash flooding across New England as a convective complex pushes through
the region producing heavy rainfall rates on top of already wet soils. As
a result, a Slight Risk of Excessive Rainfall has been hoisted for the
region on Thursday.

Further west, heat will also be of concern throughout the Central Plains,
Upper Mississippi Valley, Ohio Valley, and Midwest as daytime high
temperatures approach and exceed 100 F through the end of the week.
Widespread Heat Advisories are in effect through Friday evening as
dangerous heat indices of 105 F to 110+ F are expected. Some relief is in
sight for portions of the Midwest as another frontal system is forecast to
push south from Canada, triggering showers and thunderstorms in the Upper
Midwest and Great Lakes Thursday afternoon into Friday. Showers and
thunderstorms will then expand into the Northeast and Mid-Atlantic late
Friday into Saturday.

Elsewhere, daily diurnal showers and thunderstorms are forecast to persist
across the Four Corners region and along the sea breeze in the South and
Southeast, as the record-setting heat wave will continue in the Southwest
through the end of this week.


Russell

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