Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0133 PM CST Tue Dec 17 2024
Valid 172000Z - 181200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PARTS OF
NORTHEAST TEXAS/SOUTHEAST OKLAHOMA TO WESTERN TENNESSEE...
...SUMMARY...
Isolated strong to severe thunderstorms are possible tonight through
early Wednesday morning across parts of northeast Texas and vicinity
into western Tennessee.
...20z Update...
No changes are needed to the D1 Convective Outlook. See previous
discussion below for more information.
..Thornton/Gleason.. 12/17/2024
.PREV DISCUSSION... /ISSUED 1030 AM CST Tue Dec 17 2024/
...Synopsis...
Gradual trough amplification will occur through the period across
the Plains into the Midwest, as a shortwave trough digs from the
central Rockies to the southern Plains tonight. At the surface, a
weak cyclone should develop from the central High Plains to the
Mid-South and lower OH Valley by early Wednesday morning. Greater
low-level moisture, characterized by upper 50s to mid 60s surface
dewpoints, is in place across parts of the ArkLaTex to northern MS
along/south of a convective outflow boundary/front. This moisture is
forecast to spread gradually northward through tonight ahead of the
approaching shortwave trough. A separate cold front will spread
east-southeastward over parts of the southern Plains and mid MS
Valley/Mid-South this evening and overnight.
...Northeast Texas to Western Tennessee...
Robust convective development will likely be delayed until
near/after 05Z tonight, as low-level warm advection and large-scale
ascent preceding the upper trough gradually overspread the warm
sector. Even though steeper mid-level lapse rates should lag/remain
generally north of the cold front, weak instability (around 500-1000
J/kg MLCAPE) should be present in a narrow corridor along and just
ahead of the front. This instability will become weaker and more
limited with northeastward extent into middle TN, with an
ill-defined cutoff to isolated severe potential somewhere in the
western to middle TN vicinity.
Strengthening mid-level southwesterly flow with the amplifying upper
trough will eventually move into the ArkLaTex and Mid-South, mainly
after 06Z, in tandem with modestly enhanced low-level
southwesterlies. Sufficient speed shear should exist to support some
updraft organization, although the orientation of the deep-layer
shear vector will be nearly parallel to the surface front.
Thunderstorm mergers and interactions appear likely, with eventual
upscale growth into a line anticipated as the cold front intercepts
the greater low-level moisture, especially after 09Z. Isolated hail
may occur with initial convective development, before strong to
occasionally damaging winds become the main threat in the last few
hours of the period with the line. A brief tornado cannot be ruled
out. The overall severe threat should remain isolated due to the
somewhat marginal thermodynamic environment.
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