SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0657 AM CST Tue Dec 31 2024
Valid 311300Z - 011200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
APPALACHIANS TO PARTS OF THE MID-ATLANTIC...
...SUMMARY...
Damaging to isolated marginally severe gusts, isolated large hail,
and possibly a brief tornado, are possible today from the central
Appalachians to parts of the Mid-Atlantic.
...Synopsis...
In mid/upper levels, a progressive shortwave pattern will persist
within a broadly cyclonic flow field covering much of the CONUS from
the Rockies eastward. The most important of these features for
convective potential will be a well-developed shortwave trough --
evident in moisture-channel imagery from a low over IL south-
southeastward to western portions of KY and the lower Tennessee
Valley region. Though the 500-mb low may not remain closed, the
trough will remain strong and shift east-northeastward up the Ohio
Valley today, reaching OH, WV and the western Appalachians of VA/NC
by 00Z. The trough should pivot over the northern Mid-Atlantic and
offshore from the Delmarva Peninsula by 12Z.
At the surface, 11Z analysis showed a low between CMI-MTO, related
to the shortwave trough aloft, a cold front arching southwestward
across western parts of TN/KY, and a warm front east-southeastward
across northeastern KY that will shift northeastward over portions
of WV and southern OH through the early afternoon, as the low
occludes and moves northeastward. By 00Z, the low should reach the
CLE area, with cold front moving eastward across western parts of VA
and NC, and warm front moving north up the Atlantic Coast and across
the Delmarva Peninsula. An older frontal zone, now well offshore,
should continue to weaken, with considerable theta-e advection
occurring to its west near the coast.
...Central Appalachians to Mid-Atlantic...
Episodic lines and clusters of thunderstorms are expected to move
eastward across the outlook area today, from the northern
Cumberland/southern Allegheny Plateau region eastward toward coastal
Delmarva and vicinity, with occasional strong/isolated severe gusts
and hail the main severe modes, but with marginal tornado threat as
well.
Large-scale ascent will spread over this region in the form of
strong midlevel DCVA/cooling immediately preceding the trough, as
well as the peripheral/ageostrophic influences of the left exit
region of a strong 250-300-mb jet, centered from the Ozarks to the
western Carolinas. Associated destabilization aloft will offset
modest (but diurnally steepening) low-level lapse rates and marginal
moisture behind the offshore front. This yields an area of 100-300
J/kg MLCAPE already apparent in objective analyses between RAOBs,
over southern IN, despite cool surface conditions. This weakly
buoyant regime is forecast to expand and strengthen somewhat
(300-600 J/kg) as it moves eastward over eastern KY late this
morning into midday. Long, somewhat curved low-level hodographs and
strong low-level shear are expected, supporting potential for
embedded/low-topped supercells, as well as LEWP/bow features with
any linear modes.
The area of large-scale lift and accompanying strong-severe
convective potential then will shift across WV to VA/MD/DC and the
Delmarva region, encountering theta-e advection from a modified
post-frontal airmass over the Atlantic. This regime then should
move offshore, where even more-extensive convective development is
likely overnight. The wind and tornado areas have been shifted
south out of most of PA, where the low-level stable/inversion layer
should hold, and expanded westward into portions of eastern KY,
where surface-based buoyancy will exist as the cold-core region
moves overhead. Severe potential probably will be discontinuous
across this corridor, and a lack of more-robust buoyancy precludes
more than a marginal unconditional severe threat for this outlook
cycle.
------------------
...Epilogue (RE)...
This is my final SPC outlook, forecast and shift. With a
cyclonically swirling storm of memories, I retire mourning the end
of a rewarding era, yet ever grateful, blessed with a career of
public service devoted to excellence. For a poor kid from
inner-city east Dallas, carrying a passion for tornadoes from
earliest awareness, and a relentless drive to research and forecast
them, it has been everything the dream promised, and more. I hope
the American taxpayers have found my time worth their money.
Even through this autumnal transition of life's seasons, I'll stay
as inspired as ever by the tempestuous sky above -- to observe,
photograph and study it, and keep giving back to the science in some
way, as long as physically and mentally able. It just won't be on
rotating shifts. The forecasting baton passes to another generation
of sharp minds, just as the lead crew in the 1990s did for us "young
pups of SELS" in Kansas City. The SPC is in great hands.
There isn't enough room here to thank everyone from early childhood
through OU, NSSL, NHC, NSSFC/SELS, and SPC -- family, friends,
instructors, mentors, students, and colleagues -- but be assured I
do. Nothing has granted greater career fulfillment than to deliver
severe-weather forecasts with detailed, science-based insights,
customized for each situation, shift after shift for over three
decades, and to write related research papers. Thanks for reading
and using them, any or all. Stay weather-aware!
..Edwards/Grams.. 12/31/2024
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