SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0639 AM CST Thu Nov 28 2024
Valid 281300Z - 291200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHEAST U.S....
...SUMMARY...
A few strong to potentially severe thunderstorms are possible today
across parts of the Southeast.
...Synopsis...
In mid/upper levels, a couple slow-moving cyclones -- over SK and
the James Bay region of eastern Canada -- will anchor a broad area
of cyclonic flow that will cover most of the CONUS east of the
Rockies. Embedded within that flow belt is a positively tilted
shortwave trough, evident in moisture-channel imagery from southern
OH to the Ozarks. Today, this feature should move quickly eastward
and northeastward while elongating, and should extend from New
England to the Delmarva Peninsula and NC/VA border region by 00Z,
before ejecting offshore.
At the surface, a cold front was drawn at 11Z from western WV over
northwestern GA, central AL, southern MS, southwestern LA, and TC
coastal shelf waters to deep south TX. This front should proceed
eastward and southeastward today, reaching a 00Z position near an
HSE-CHS-TLH line and southwestward across the Gulf. By the end of
the period, the front should be offshore from all but central FL.
...Southeastern CONUS...
An ongoing band of convection, with widely scattered to scattered
embedded thunderstorms, was noted mainly ahead of the cold front,
from western SC to southern MS. This activity should proceed
eastward over the outlook area through the day, with isolated
damaging gusts, hail near severe limits possible. A brief tornado
or two may occur, conditional on storm-scale processes and local
convective interactions.
The shortwave trough and associated DCVA will remain north of the
outlook area and behind the surface cold front, substantially
limiting large-scale support outside very subtle height falls that
may extend southward to near a MGM-MCN-CHS line. With the strongest
isallobaric forcing located well north/northeast of the area (and
moving away), warm-sector surface winds that are not already west-
southwesterly should veer that way with time, limiting low-level
convergence/lift. This casts considerable uncertainty on convective
coverage and duration -- especially in the free warm sector.
However, sufficiently strong midlevel flow will remain to yield
favorable deep speed shear for any activity that can mature enough
to take advantage. Lengthy low-level hodographs with some curvature
should remain ahead of the front, even as the hodographs as a whole
veer clockwise with respect to the origin. This should yield 100-
200 J/kg SRH in the lowest km, and effective SRH increasing from
south to north, with peak values near 300 J/kg. Peak/preconvective
MLCAPE should reach 1000-1500 J/kg from the Gulf Coast to parts of
SC, diminishing northeastward substantially from there. The overall
severe threat should diminish this evening and tonight as lift and
instability both weaken, and the hodograph-stretching LLJ pulls away
across Atlantic waters.
..Edwards/Leitman.. 11/28/2024
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