Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
311 PM EDT Thu Sep 07 2023

Valid 00Z Fri Sep 08 2023 - 00Z Sun Sep 10 2023

...There are Slight Risk of severe thunderstorms over parts of the
Northeast and Mid-Atlantic/Central Appalachians today and tomorrow, with a
risk tomorrow (Friday) as well over the Lower Mississippi River Valley...

...There are  Excessive Heat Warnings over parts of Northeast Texas
including Dallas/Fort Worth, as well as, the Southwest Deserts of Arizona
and California into Saturday. Heat Advisories cover much of the rest of
Texas into the Lower Mississippi Valley and across the Mid-Atlantic and
New England today...

...Air Quality Alerts over parts of the Central Plains, Upper Mississippi
Valley and Red River Valley of the north...


The strong mid to upper level flow will continue to press eastward across
Southeast Canada, helping to press a cold front through the Great Lakes
into the Northeast today into tomorrow.  Given the flow weakens aloft, the
front starts to stall across the Appalachian chain into the easter slopes
leaving unsettled weather likely across the eastern US, this will press
the extreme heat offshore by Saturday; though temperatures should moderate
a bit on Friday compared to today.  High temperatures and very high
humidity continues to support Heat Advisories to continue today for much
of the Mid-Atlantic into New England supporting the potential for
scattered severe thunderstorms with incidents of large hail and damaging
winds as the primary threat.  The Storm Prediction Center (SPC) has issued
a Slight Risk today from VT/E NY into Northern Virginia with a Marginal
Risk extending into the Florida Panhandle.  Some of these may induce
localized very heavy rainfall and widely scattered instances of flash
flooding (Weather Prediction Center has issued a Marginal Risk of
Excessive Rainfall for similar areas).  A similar Slight risk from SPC and
Marginal Risk from WPC will exist tomorrow/Friday, though more confined to
the Mid-Atlantic and Northeast.   By Saturday, the much of the highest
heat, unstable air is likely to have been pressed east further limiting
severe threats even though there should be scattered showers/thunderstorms
along/ahead of the stalled front.


Further south across the Gulf Coast, the same frontal system will press
into and through the Florida Panhandle today, but a weak surface wave
along the eastern side of the persistent Upper-level ridge/Heat Dome will
keep very high temperatures (over 100-105F) nearly 20-25 degrees above
normal to once again bake northern Texas.  Excessive Heat Warnings are in
effect for much of northeast Texas, including the Dallas/Fort Worth
region. These are very dangerous conditions to be outside for prolonged
periods, seek shade and keep hydrated if required to be outdoors today and
into tomorrow (Friday).   Nearer the coast, the return flow will be off
the Western Gulf of Mexico and bring higher dewpoints and potential for
increased thunderstorm activity across southeast Texas into the Lower
Mississippi Valley.  SPC has a Slight Risk of severe thunderstorms for
Friday from the Texarkana Region though the Sabine River Valley.  If there
is some positive outlook, the center of the ridge will press westward into
New Mexico by late Friday/Saturday allowing for the front to drop south. 
However, this will just press the above average heat toward the
Boarderlands with Mexico, and increase high heat for the desert southwest.
 Temperatures will once again reach the 110s and the National Weather
Service forecast offices have hoisted an Excessive Heat Warning for
Saturday into Sunday for parts of southeast California and southern
Arizona, including Palm Springs, Yuma, Phoenix and Tucson.


Elsewhere, behind the front, the Great Lakes and Ohio Valley should see a
reprieve from the heat with even unseasonably cool air bringing highs in
the 60s and lower 70s nearing 80 along the Ohio River today and tomorrow,
generally 5-15 degrees below normal.

Additionally, air quality alerts remain in effect across portions of the
central Plains, Mid-Missouri Valley and the Red River of the North, due to
some stagnant air but also return of thicker Canadian Smoke that is
drifting downward toward the surface increasing respiratory strain.   The
good news, a cold front across the High Plains of MT/Southern Prairies of
Canada will continue to drop southward over the next few days.  While
there is some smoke likely behind the front, a much cooler airmass and
faster moving air may allow for some modest improvement with less
stagnation.  Temperatures by Saturday will be only into the 70s and spots
of upper 60s for highs across the Dakotas (above 10 to 20 degrees below
average).

Gallina


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