Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
400 AM EDT Tue Aug 15 2023

Valid 12Z Tue Aug 15 2023 - 12Z Thu Aug 17 2023

...Dangerous heat continues across the Pacific Northwest into the Northern
Rockies as much of the South sees a brief reprieve from recent oppressive
heat...

...Flash flooding and severe thunderstorms possible for portions of the
coastal Mid-Atlantic and Carolinas Tuesday...

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

A dangerous heat wave will continue in the Pacific Northwest/Northern
Rockies as a strong ridge of high pressure remains in place aloft, with
most of the region under heat-related advisories and warnings. High
temperatures will be in the low to mid-100s for most interior locations,
with 90s around Puget Sound. Numerous near record-tying/breaking highs are
possible. Overnight lows will be near record-tying/breaking warm levels as
well, providing little relief form the heat overnight. 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. Meanwhile, some relief from the
oppressive heat has finally come to northern portions of the South and
will continue through midweek as a cold front pushes through the region.
Highs on Tuesday from northern Georgia west through north Texas will drop
below seasonable averages in the mid-80s to low 90s. Oppressive heat will
remain in place to the south of the front along portions of the coastal
Carolinas southwestward to Texas along the Gulf Coast. Highs will be in
the mid-90s in the coastal Carolinas, Southeast, and Florida, with upper
90s to low 100s possible for central and western portions of the Gulf
Coast. These temperatures when combined with high humidity will allow for
sultry heat indices as high as 110 to 120F for many locations. Numerous
record-tying/breaking highs are forecast. However, the cold front will
continue southward on Wednesday, bringing a brief reprieve from the
central Gulf Coast eastward to the Carolinas as well. Highs will remain
summer-time hot but be closer to seasonable averages. Unfortunately,
portions of the western Gulf Coast and far south Texas will remain south
of the cold front and not see any relief. The relief looks to be brief as
well, particularly for portions of Texas, where 100s are forecast to
return to most locations by Thursday.

To the north, additional showers and thunderstorms are expected Tuesday
along coastal portions of the Mid-Atlantic and Carolinas which remain
ahead of the slowly moving frontal boundary. Seasonably high moisture in
place will help lead to the risk for some locally heavy downpours, with a
Slight Risk of Excessive Rainfall (level 2/4) in place for the risk of a
few scattered instances of flash flooding. In addition, the Storm
Prediction Center has also outlined a Slight Risk for severe weather
(level 2/5) as moderately strong flow aloft associated with an upper-level
wave passing overhead will provide enough deep shear for a few more
robust, organized storms capable of producing some damaging winds.
Additional storms with a more isolated risk of flash flooding and severe
weather will be possible north into coastal New England and southwestward
to portions of the central Gulf Coast east through the Florida Big Bend.
The front will become nearly stationary by Wednesday, allowing for
additional storm chances from the coastal Carolinas southwestward to
Florida with a continued risk of isolated flash flooding. Another frontal
system will consolidate/organize over south-central Canada and the
Northern Plains/Upper Midwest through the day Tuesday and overnight
Wednesday and bring a chance for some thunderstorms to the Upper Midwest
Wednesday. A Slight Risk of severe weather is in place as moist return
flow ahead of a cold front will provide enough buoyancy ahead of the front
for some potent storms, with the main threat damaging winds and perhaps
some large hail as storms will likely organize into a line along the
front. Highs behind the cold front will remain much below average Tuesday
for many locations in the Midwest and Northeast/New England, with mainly
70s expected. Temperatures will rebound into the low 80s outside of New
England on Wednesday. Highs will be much warmer following more moderation
further west, with upper 80s to low 90s for the Northern/Central Plains.
Some locations from the Central High Plains northeastward to the
Middle/Upper Missouri Valley will jump into the upper 90s Wednesday.

Daily rounds of Monsoonal showers and thunderstorms are forecast across
the Four Corners region northwestward into the Great Basin and for
portions of the Sierra, with locally heavy downpours possible and an
isolated threat for flash flooding. Daily highs will be a bit below
seasonable averages around the Four Corners due in part to precipitation
chances, with upper 70s to mid-80s. Otherwise, highs will be near to a bit
above seasonal averages more broadly in the region with 70s along the
California Coast, low to mid-90s for the Great Basin and Central/Southern
Rockies, and 100s to low 110s for the Desert Southwest. Highs in the
interior California valleys will trend a bit hotter with mid-100s expected
and Heat Advisories in place.

Putnam

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