Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
402 AM EDT Wed Jul 12 2023

Valid 12Z Wed Jul 12 2023 - 12Z Fri Jul 14 2023

...Additional rounds of severe weather and flash flooding persist across
the Midwest, Mississippi Valley, and Plains over the next couple days...

...Heavy rain potential returns to the Northeast Thursday...

...Building heat wave continues to expand across much of the southern tier
of the U.S....

A complex Summer-time setup continues to unfold across the central U.S.
with multiple corridors of severe weather and heavy rainfall expected
Wednesday. A shortwave will rotate around the base of a broad Hudson Bay
low providing broad assent over a slow-moving surface frontal system
draped through the Midwest/Mississippi Valley/Plains. Deep Gulf moisture
pooling along and to the south of the boundary and warm summer-time
temperatures will provide the instability for widespread robust
thunderstorm development producing efficient heavy rainfall throughout
much of the Midwest/Mississippi Valley. Ongoing convection early Wednesday
morning as well as additional convection that forms will also likely lead
to multiple outflow boundaries providing additional focused areas of storm
development leading to multiple corridors of heavy rainfall totals and the
risk for flash flooding. Currently, a Moderate Risk of Excessive Rainfall
(level 3/4) is in effect Wednesday for portions of far southwest Arkansas
and northwest Louisiana where heavy rainfall overnight has led to very
sensitive ground conditions with additional heavy rainfall expected,
posing a locally increased risk of scattered to widespread instances of
flash flooding. A broad Slight Risk (level 2/4) extends into the Lower
Mississippi Valley and central Gulf Coast, with additional Slight Risks
covering portions southeast Kansas/southwest Missouri as well as portions
of the Upper Mississippi Valley and Lower Great Lakes. There is also a
broad Slight Risk of severe weather (level 2/5) outlined by the Storm
Prediction Center covering the Middle/Lower Missouri and Middle
Mississippi Valleys where some of the more robust and organized
storms/convective systems may produce some large hail and damaging winds.
As the initial shortwave departs to the east, less activity is expected
Thursday, although some additional locally heavy rainfall and a severe
thunderstorm or two will remain possible across the area as the frontal
boundary and buoyant Summertime airmass continue to remain in the region.
Temperatures will be hot ahead of the front but will be much below average
behind it on Wednesday. Highs will be in the upper 60s to mid 70s for much
of the Northern Plains and Great Lakes Region. Temperatures will rebound
on Thursday for most locations into the upper 70s to mid 80s.

The upper-level shortwave as well as surface frontal system will translate
eastward Thursday towards the East Coast, bringing returning chances for
thunderstorms and heavy rainfall from the Ohio Valley into the Northeast.
Mean southerly flow in the low levels ahead of the system will draw
moisture back northward across the region, helping to fuel heavy
downpour-producing showers and thunderstorms. Slight Risks of Excessive
Rainfall have been outlined for portions of Upstate New York and interior
New England as well as the Upper Ohio Valley. Interior New England remains
particularly sensitive to any additional rainfall following significant
rainfall earlier this week, with additional instances of flash flooding
more likely. Showers and thunderstorms are also expected through the
Tennessee Valley and into the Southeast with some locally heavy rainfall
possible. Forecast high temperatures will be a bit above average and
Summer-time hot throughout the region with mid to upper 80s for New
England, the interior Northeast, and the Ohio Valley and low to mid-90s
for the Mid-Atlantic, Carolinas, and Southeast.

Meanwhile, a stagnant upper-level high in place over the
Southwest/northern Mexico will not only remain in place but begin to build
in coverage, particularly to the northwest over the Great Basin and
California. Widespread heat-related advisories and warnings remain in
place across the Central/Southern Plains and Lower Mississippi Valley as
well as portions of the Desert Southwest and California. For locations
further east in the Plains and into the Lower Mississippi Valley,
temperatures in the upper 90s and low 100s combined with high humidity
will make it feel like 105-110 degrees, locally as high as 115 on
Wednesday. Temperatures look to fall a bit on Thursday bringing a bit of
relief to portions of the Central and Southern Plains, while conditions
remain hot in Texas. Similarly hot conditions will be in place to the west
as humidity values will be lower but air temperatures soar into the mid to
upper 100s for west Texas and portions of the Southwest and into the 110s
in the Desert Southwest. A few record-tying/breaking highs are possible
for west Texas on Wednesday. The heat will begin to build into the Great
Basin and interior California on Thursday, with highs rising into the
mid-90s to low 100s. Unfortunately, the long term outlook for the region
shows a continued heatwave through this weekend and into next week. While
not notably higher than average, a continued uptick of temperatures into
the mid-90s are relatively high and near record-tying/breaking levels for
the Florida Peninsula. When combined with the humidity, it will feel like
105-110 degrees. Elsewhere, conditions will be generally tranquil with
near-average high temperatures for the Northwest ahead of hotter
tempreatures expected this weekend. 

Putnam


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