Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0654 AM CST Thu Feb 22 2024
Valid 221300Z - 231200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
THE MID-SOUTH REGION...
...SUMMARY...
Thunderstorms may produce marginally severe gusts or hail this
afternoon and evening over parts of the Mid-South region.
...Synopsis...
In the mean, mid/upper-level pattern amplification should begin
again during this period, as ridging builds over NV, the Pacific
Coast States and interior Northwest. Downstream, a series of
shortwaves will contribute to substantial synoptic-scale height
falls over much of the Mississippi and Ohio Valleys to the central
Gulf Coast. None of those perturbations -- including some apparent
in moisture-channel imagery over OK, northern KS/NE, and western CO
-- are (or will become) particularly intense, but should contribute
to at least weak large-scale destabilization aloft and maintenance
or strengthening of cyclonic flow.
At the surface, 11Z analysis showed a cold front extending from a
low over southeastern ON across northern IN, through weak lows over
central MO and near TUL, then across northwest TX to southern NM.
The front should move eastward and southeastward today, to a 00Z
position over eastern/southern OH, the lowest Ohio Valley, eastern/
southern AR, and northeast to south-central TX. By 12Z, the front
should reach central NY, eastern PA, the southern Appalachians,
central parts of MS/LA, and shelf waters of the northwestern Gulf.
...Mid-South region...
Isolated to widely scattered thunderstorms are expected to develop
by late this afternoon along/ahead of the cold front, over central/
eastern AR and perhaps western TN. Activity should strengthen and
increase in coverage through evening as it encounters greater
moisture across the Mississippi Valley and into northern portions of
MS tonight. Some upscale organization into a short QLCS is possible
from early multicell to supercell modes. Marginally severe hail and
damaging gusts will be the main concerns.
The outlook area will reside on the southwestern rim of a far larger
swath of general thunderstorm potential, but with access to
sustained, effectively surface-based and at least marginally moist
inflow parcels beginning mid/late afternoon in AR and shifting east-
southeastward with time. Progs that generate little substantial
convection generally are too cool at the surface. Forecast max
surface temperatures in the mid/upper 60s F over much of the area
will support favorable low-level lapse rates, as well as some
boundary-layer mixing, amidst potential for localized downward
momentum transfer from stronger flow aloft, for gust support.
Midlevel lapse rates are not expected to be very strong, limiting
MLCAPE to around 250-750 J/kg, and likely keeping the hail potential
isolated, marginal and conditional to supercell maturation.
Sufficient deep shear will exist for that, however, with modified
forecast soundings indicating around 40-450-kt effective-shear
magnitudes and 150-250 J/kg effective SRH -- despite prefrontal
veering with time of surface winds toward southwesterly. Greater
diurnal boundary-layer mixing/drying, EML-related CINH and weaker
CAPE will likely restrict severe potential around western parts of
the outlook, while instability decreases northward, moisture
decreases eastward, and lift weakens southward.
..Edwards/Mosier.. 02/22/2024
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