ACUS01 KWNS 311939
SWODY1
SPC AC 311938

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0138 PM CST Tue Dec 31 2024

Valid 312000Z - 011200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
APPALACHIANS TO THE MID ATLANTIC...

...SUMMARY...
Damaging gusts, isolated hail, and a brief tornado remain possible
this afternoon from the central Appalachians into parts of the
Mid-Atlantic.

...20z Update...
The previous forecast remains valid with minimal changes. The
western edge of the Marginal Risk area has been removed from
portions of eastern KY and western WV, as the aforementioned upper
trough has moved eastward. Weak buoyancy (200-400 J/kg MUCAPE) is
present across parts of WV and VA where clear skies have allowed
surface temperatures to warm to near 60 F beneath the mid-level cold
core. Despite very minimal surface moisture (dewpoints in the 30 to
40s F) steep mid and low-level lapse rates (7-7.5 C/km) will
continue to allow for 35-50 kt of 0-3 km flow to mix down to the
surface. Several gusts of 45+ kt have been observed with low topped
convective bands ahead of and along the cold front. As these storms
move eastward, they will continue to pose a risk for damaging winds
through the afternoon. Isolated small hail and perhaps a brief
tornado also remain possible with any stronger rotating cells, given
relatively strong low-level speed shear. See the prior discussion
and MCD 2322 for more info.

..Lyons.. 12/31/2024

.PREV DISCUSSION... /ISSUED 1025 AM CST Tue Dec 31 2024/

...KY to the Mid Atlantic Region...
A potent, negatively-tilted shortwave trough will move from the
upper OH Valley into NY/PA today, with an associated 80-100 knot
mid-level speed max nosing across the Carolinas.  Strong large-scale
forcing and low-level warm advection is resulting in sufficient lift
for the development of multiple lines/clusters of low-topped
convection (some with lightning) across parts of OH/KY/TN/WV.  This
activity will move quickly eastward through the day across the
central Appalachians and into the Mid Atlantic region this
afternoon/evening.

Forecast soundings show cold mid-level temperatures, resulting in
steep lapse rates aloft.  This will continue to support a threat of
thunderstorms through tonight.  Low-level moisture is quite limited,
and forecast CAPE values are below 500 J/kg.  Nevertheless,  low and
mid-level wind fields are very strong, which could easily mix down
within any more-organized convection.  Low-level shear is also
strong enough to support updraft rotation (as already noted in a few
cells this morning in KY) which could pose a risk of a brief tornado
or occasional hail through the period.

$$

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