SPC Dec 16, 2024 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0200 PM CST Mon Dec 16 2024

Valid 162000Z - 171200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE ARK-LA-TEX AND LOWER TO MID MISSISSIPPI VALLEY...

...SUMMARY...
Isolated strong to severe thunderstorms with mainly a damaging wind
threat may occur today across parts of the ArkLaTex into western
Tennessee and vicinity. Some hail may also occur.

...20Z Update...
The previous forecast remains on track. Only minor adjustments to
the lines have been made for this Day 1 outlook update. A cold
front, located from north-central Texas to southeast Missouri, will
continue to move southeastward. Ahead of the front, a moist airmass
with surface dewpoints in the 60s F, will be unstable enough for a
few strong storms this afternoon into early evening. Moderate
deep-layer shear will support isolated severe storms capable of
marginally severe wind gusts and hail. The wind-damage threat will
be located from far northeast Texas into western Tennessee. The hail
threat will be primarily focused across the Ark-La-Tex where the
stronger instability is currently located.

..Broyles.. 12/16/2024

.PREV DISCUSSION... /ISSUED 1028 AM CST Mon Dec 16 2024/

...Synopsis...
The upper trough over the northern Plains and Upper Midwest will
move across the Great Lakes today. Related surface cyclone will
develop eastward over northern Ontario, with a trailing cold front
advancing east-southeastward across parts of the OH Valley,
Mid-South, and southern Plains. The western portion of this front
will stall and weaken across the ArkLaTex into central TX by this
evening.

...ArkLaTex into the Mid-South...
Scattered to numerous showers and thunderstorms are ongoing this
morning across parts of northern AR into the lower OH Valley,
generally along/near the front. Current expectations are for the
better forcing associated with the upper trough to remain mostly
displaced to the north of the warm sector through the day, with
limited low-level convergence along the cold front and modest
low-level warm advection persisting. Latest visible satellite
imagery also shows low cloud cover remaining prevalent across much
of the ArkLaTex and Mid-South/lower MS Valley. These clouds will
likely hinder daytime heating to some extent. Modest mid-level lapse
rates were also noted on the 12Z soundings at SHV/LZK, with somewhat
better lapse rates aloft at FWD.

Even with these limitations regarding forcing and instability, most
guidance continues to show around 500-1000 J/kg of MLCAPE
along/ahead of the cold front from northeast TX into AR and western
TN by mid afternoon. A gradual uptick in convective coverage and
intensity should occur through the afternoon across these areas,
with modest but sufficient deep-layer shear (25-35 kt) for some
updraft organization. Most 12Z HREF guidance shows small clusters
developing and spreading east-southeastward through the early
evening. Even though low-level lapse rates will probably remain poor
due to the limited daytime heating, there still appears to be enough
of a signal to support inclusion of a Marginal Risk, mainly for
isolated damaging winds. Some hail may also occur across northeast
TX into AR, where greater instability should be present.

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