SPC AC 180054
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0654 PM CST Tue Dec 17 2024
Valid 180100Z - 181200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE ARK-LA-TEX AND MID MISSISSIPPI VALLEY...
...SUMMARY...
Marginally severe thunderstorms associated with isolated severe
gusts and hail will be possible from late this evening into early
Wednesday morning from parts of the Ark-La-Tex into the mid
Mississippi Valley.
...Ark-La-Tex/Mid Mississippi Valley...
A mid-level trough will move southeastward across the central U.S.
tonight, as an associated cold front advances southeastward into the
Ark-La-Tex and mid Mississippi Valley. Ahead of the front, moisture
advection will gradually increase surface dewpoints into the lower
to mid 60s F from northeast Texas to western Tennessee. In response,
destabilization will take place ahead of the front with MUCAPE
increasing into the 1000 to 1500 J/kg range. As low-level
convergence strengthens near the front late this evening, scattered
thunderstorm initiation is expected. As cell coverage increases, a
line of storms will likely develop just ahead of the front around
midnight. This line is forecast to move southeastward across the
Ark-La-Tex and mid Mississippi Valley during the overnight period.
RAP forecast soundings after midnight near the expected location of
the line in northeastern Arkansas have a temperature inversion in
the boundary layer, with instability primarily located above 700 mb.
This elevated instability combined with effective shear of 30 to 40
knots may be enough for a marginal severe threat overnight as the
low-level jet gradually strengthens. Severe gusts and hail will be
the primary threats, especially if cells can become surface-based
within the stronger low-level flow. As the line moves southeastward
across eastern Arkansas and western Tennessee late tonight into
early Wednesday morning, a brief tornado will also be possible.
However, low to mid-level lapse rates are forecast to be poor, which
will help to limit the severe weather risk.
..Broyles.. 12/18/2024
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0600Z
SPC AC 171730
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1130 AM CST Tue Dec 17 2024
Valid 181200Z - 191200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE TENNESSEE VALLEY...
...SUMMARY...
Isolated damaging wind gusts and a brief tornado are possible
through mid-day Wednesday across portions of the Tennessee Valley.
...Synopsis...
A positively tilted upper trough will develop east across the
eastern U.S. on Wednesday. Moderate mid/upper level southwesterly
flow ahead of the trough will overspread the OH/TN Valleys into the
Carolinas and Mid-Atlantic regions. At the surface, a cold front
will extend from southern OH to southeast AR to central TX at the
beginning of the period. This front will develop southeast across
the Southeast and Mid-Atlantic, mostly moving offshore from the Gulf
and Atlantic coasts by Thursday morning.
...Northeast Texas to the Tennessee Valley...
Thunderstorms will be ongoing along a frontal zone from northeast
Texas to western Tennessee at the beginning of the forecast period.
These storms will likely be mostly anafrontal due to the
southeastward advancing cold front and storm motion parallel to the
front. In addition, these storms should already be in their
weakening phase by 12Z as they outrun the better low-level
instability. The only exception will be across western/middle
Tennessee between 12 and 18Z where some instability will remain and
stronger flow could promote more organization/propagation ahead of
the cold front. A damaging wind gust or a brief tornado cannot be
ruled out early in the forecast period. Despite the weakening
instability through the morning, some damaging wind threat could
persist into parts of eastern Tennessee and far southern Kentucky
through mid-day as the low-level jet strengthens to over 50 knots
during the morning hours.
...FL/GA/Carolinas...
Southerly flow ahead of the approaching mid-level trough will
establish low to mid 60s dewpoints across much of Florida into
eastern Georgia and the eastern Carolinas by Wednesday afternoon.
Weak to moderate instability is expected within a broad region of
weak isentropic ascent across the region. Upper-level forcing will
lag well behind the front which should keep any thunderstorm
development isolated. However, if any storms develop, they could
have some marginal hail/wind threat given moderate instability and
shear present across the region Wednesday afternoon. Storm coverage
concerns related to weak forcing are the primary limiting factor to
severe weather probabilities at this time.
..Bentley.. 12/17/2024
WUUS02 PTSDY2
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0700Z
SPC AC 171913
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0113 PM CST Tue Dec 17 2024
Valid 191200Z - 201200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Severe thunderstorms are not expected on Thursday.
...Synopsis...
A positively tilted mid-level trough will move from the Southeast
CONUS to the western Atlantic on Thursday. In addition, another
mid-level trough will dig south out of the Canadian Prairies into
the Upper Midwest while a ridge translates across the western CONUS.
A surface cold front will begin the period across northern Florida
and move south along the peninsula during the day.
...Florida...
Weak to moderate instability will develop ahead of the surface front
as it moves south along the Florida Peninsula during the day. Some
thunderstorms will be possible along the eastern and southern coast
of Florida during the afternoon where convergence and instability
will be maximized. However, lapse rates will be too weak to support
any severe weather potential.
..Bentley.. 12/17/2024
WUUS03 PTSDY3
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0830Z
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