LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1153 PM CST Tue Feb 28 2023
Valid 011200Z - 021200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
TEXAS TO THE TENNESSEE VALLEY...
...SUMMARY...
Severe thunderstorms will be possible on Wednesday from northeast
Texas through the Mid-South and into Middle Tennessee, with a threat
of hail, damaging wind, and a couple of tornadoes. Additional strong
to isolated severe thunderstorms capable of wind damage will be
possible across the Ohio Valley vicinity.
...Synopsis...
A potent large-scale mid/upper trough will dig south and east across
the western U.S. today. Ahead of the trough, fast southwesterly
mid/upper flow will overspread TX to the Mid-South/Ohio Valley and
eventually the Mid-Atlantic. A subtle shortwave impulse ejecting
ahead of the western trough is expected to migrate through this fast
southwesterly deep-layer flow from the Arklatex through the TN/OH
Valley vicinity. Ahead of the ejecting shortwave impulse, southerly
low-level flow will transport boundary-layer moisture northward
across the TN/OH Valleys, and strong to severe thunderstorm
development is expected this afternoon into the evening.
...TX to the TN Valley vicinity...
A stalled front is forecast to reside from eastern OK into central
TX early this morning. Weak ascent associated with the lead
shortwave trough and convergence along the stalled front may be
sufficient for isolated, elevated thunderstorms this morning across
a narrow corridor from central TX into north TX. These initial cells
could produce hail. Limited storm coverage and somewhat conditional
threat will preclude higher severe probabilities across this portion
of TX.
By afternoon, stronger heating and moistening, coupled with
increasing forcing for ascent from the Arklatex into the Mid-South
will result in erosion of the midlevel cap. Isolated supercells are
expected by mid/late afternoon along a front extending from
northwest AR into the Ohio Valley. Elongated forecast hodographs
amid effective shear values greater than 45 kt suggest splitting
supercells will be possible. Large hail, some greater than 2 inches
in diameter, will be possible with these initial supercells from far
northeast TX through southern AR and into northwest MS.
With time, a modestly increasing low-level jet and forcing along the
front will support convection organizing into a line shifting east
across the Mid-South/TN Valley this evening into tonight, with an
attendant increase in damaging gust potential. Low-level shear is
forecast to be modest, but sufficient, and some curvature to
low-level hodographs suggest a couple of tornadoes also will be
possible within the line and amid any preceding cells.
Separate from initial convection further west, some guidance
suggests isolated supercells could develop from northeast MS into
northern AL and arcing southeast toward east-central AL/west-central
GA during the afternoon if sufficient heating occurs to overcome
capping. While this threat is a bit conditional, should storms
develop, a threat for damaging gusts and a couple of tornadoes would
exist.
...OH Valley Vicinity...
The Ohio Valley portion of the cold front is expected to advance
more quickly east/southeast this evening. Boundary-layer moisture
will be more modest, from the mid/upper 50s to near 60 F. However,
steep lapse rates and strong heating ahead of the front will
contribute to MLCAPE around 500-1000 J/kg. Strong storms are
expected to develop along the surging front by early evening and
track southeast across the region, producing strong to locally
damaging gusts.
..Leitman/Flournoy.. 03/01/2023
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