ACUS01 KWNS 011250
SWODY1
SPC AC 011248

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0748 AM CDT Sun Sep 01 2024

Valid 011300Z - 021200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
THE SOUTHERN APPALACHIANS INTO THE MID-ATLANTIC AND SOUTHERN NEW ENGLAND...

...SUMMARY...
Strong thunderstorms capable of producing isolated damaging winds
may occur this afternoon across parts of the southern Appalachians
into the Mid-Atlantic and southern New England.

...Southern Appalachians into the Mid-Atlantic and Southern New
England...
Thunderstorms should gradually increase in coverage this afternoon
along/south of a weak front that extends from the Mid-South/lower OH
Valley into the Mid-Atlantic. Morning visible satellite imagery
shows plentiful cloud cover near this boundary, and downstream
across parts of NC and the Mid-Atlantic into southern New England.
Still, filtered daytime heating of a moist low-level airmass should
allow at least weak instability to develop by early to mid afternoon
along and south/east of the front, even though mid-level lapse rates
will remain poor.

The glancing influence/ascent of an upper trough over eastern
Canada, along with weak orographic lift, will likely encourage
convection development through the afternoon and early evening.
Mid-level flow and related deep-layer shear are forecast to remain
fairly modest, especially with southward extent across the
Mid-Atlantic into the Carolinas and southern Appalachians. Still,
enough flow and related shear may be present to support modest
thunderstorm organization. Multiple loosely organized multicell
clusters may eventually develop and consolidate by late afternoon
and early evening, while posing some threat for isolated strong to
damaging winds as they move generally eastward. The greatest
concentration of thunderstorms should exist across parts of southern
VA into NC and upstate SC where greater instability is forecast this
afternoon. But, confidence in a more organized wind threat remains
too low to include greater severe wind probabilities.

...Western/Northern New York into Northern New England...
As the primary upper trough and related surface cold front continue
eastward across Ontario/Quebec today, daytime heating of a modestly
moist low-level airmass will occur over parts of western/northern
NY. Although poor mid-level lapse rates will likely hinder the
development of any more than weak instability across this area
(MLCAPE generally 500 J/kg of less), low/mid-level winds and related
shear in the cloud-bearing layer is expected to strengthen through
this afternoon with the approach of the upper trough. Some
high-resolution/convection-allowing model guidance shows a
low-topped line of thunderstorms developing this afternoon along or
just ahead of the cold front. As low-level lapse rates steepen with
daytime heating, some of this convection could produce isolated
strong to severe wind gusts given the strengthening low/mid-level
flow expected. The area impacted should remain fairly small across
western/northern NY (generally downstream of Lake Ontario) due to
more even more limited instability farther east across central NY
into northern New England.

..Gleason/Leitman.. 09/01/2024

$$
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