Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
353 PM EDT Sun Aug 13 2023

Valid 00Z Mon Aug 14 2023 - 00Z Wed Aug 16 2023

...Flash flooding and severe thunderstorms possible for portions of the
Plains/Mississippi Valley Sunday, shifting to the Great Lakes/Ohio
Valley/Mid-Atlantic Monday...

...The South continues its dangerous heatwave while another heat wave
begins across the Pacific Northwest Sunday...

...Monsoonal showers continue across the Four Corners region with some
locally heavy downpours possible...

The northern stream will continue to be active and unsettled as as pair of
frontal boundaries trigger numerous showers and thunderstorms from the
Plains eastward. Theses storms have potential to be quite strong, as
sufficient deep layer shear will be in place for some organized severe
storms capable of damaging winds, a few tornadoes, and large hail. They
may also dump several inches of rain. Moisture pooling between the
boundaries from portions of the Central/Southern Plains into the Middle
Mississippi Valley will help promote efficient rainfall rates with the
prospect of storms moving parallel to the fronts repeatedly over the same
region heightening the risk for several inches of rainfall. The Storm
prediction Center has an Enhanced Risk in place over the Missouri/Arkansas
Ozarks region with a broader Slight Risk spanning from the Oklahoma/Texas
panhandles to the Tennessee Valley. Additionally, WPC has a Moderate Risk
for excessive rainfall over the Ozarks region and a Slight for much of the
same area as SPC. The threat area will shift to the Great Lakes,
Ohio/Tennessee Valleys, Mid-Atlantic and the Northeast Monday and Tuesday.
Behind the cold front, cooler air will infiltrate the Northern Plains and
Upper Midwest yielding daily maximums to range from the upper 60s to lower
70s and will spread eastward into the Midwest; mid 70s to lower 80s can be
expected for portions of the Central and Southern Plains. Highs will be
closer to and above summertime averages ahead of the front, with upper 70s
and low 80s for New England and mid-80s to low 90s for the Mid-Atlantic.

In contrast, the prolonged hot spell will keep dangerous temperatures in
place for much of the South into early next week thanks to the well
anchored upper ridge. Widespread heat-related advisories and warnings span
from Florida north to the Carolinas and west to Texas/Oklahoma; with the
most excessive heat focusing over Texas and into the Lower Mississippi
Valley. Daily high temperatures are forecast to range from the mid-90s in
Florida and the Carolinas, the upper 90s into portions of the Southeast,
the low 100s in Oklahoma and the Lower Mississippi Valley, and the mid
100s into portions of Texas. These temperatures when combined with high
humidity will allow for heat indices as high as 110 to 120F for many
locations. Numerous record-tying/breaking highs are forecast both days,
with similarly record-level warm low temperatures in the upper 70s to low
80s providing little relief from the heat overnight. Some moderation of
the heat is expected for northern portions of the region by the middle of
this upcoming week as cooler air follows the southward moving cold front
cutting across the country, starting with the noted portions of the
Southern Plains Monday.

A heatwave is beginning to build in today over the Pacific Northwest in
relation to the strong ridge of high pressure overhead. Temperatures will
nearing the 100 mark today within the interior valleys west of the
Cascades in Oregon 100s and will further intensify and expand across the
region Monday. Maximum temperatures will range from upper 80s to low 90s
around Puget Sound, the upper 90s to low 100s east of the Cascades, and
the mid-100s to potentially over 110 degrees for the interior west of the
Cascades. Numerous near record-tying/breaking highs are possible here as
well. These temperatures combined with the duration of heat, expected to
continue through this week, will increasingly pose a heightened health
risk, especially for those without adequate air conditioning.  

Daily rounds of thunderstorm activity can be expected across the Four
Corners region thanks to Monsoonal moisture and a lingering frontal
boundary near the region. Any of these storms may have the potential to
produce heavy downpours which brings an isolated threat for flash
flooding. Daily highs will be near seasonal normal with 70s in proximity
of the California Coast, low to mid-90s for the Great Basin, upper 90s to
low 100s for the interior California valleys, and 100s for the Desert
Southwest. With cooler, post-frontal air filtering south into the central
U.S., portions of the Central/Southern High Plains/Rockies will have some
cooler highs than point west; mainly in the upper 70s to low 80s.

Campbell

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