SPC AC 041306
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0706 AM CST Mon Mar 04 2024
Valid 041300Z - 051200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE
SOUTHERN UPPER GREAT LAKES REGION SOUTHWESTWARD TO TEXAS...AND INTO
THE LOWER MISSISSIPPI VALLEY AREA...
Isolated strong to severe thunderstorms will be possible this
afternoon into tonight from parts of central Texas into the lower
Mississippi Valley, as well as from the Ozarks into the Midwest.
Large hail is expected to be the main threat, but strong/gusty winds
and even a tornado may also occur.
A broad area of cyclonic flow aloft will remain in place over the
western two-thirds of the country, and is expected to gradually
expand eastward with time.
As the upper troughing expands, a surface baroclinic zone extending
from the Texas Panhandle to the Upper Great Lakes will gradually
shift southeastward as a cold front, particularly during the second
half of the period. Along and ahead of this boundary, convection --
and isolated severe weather -- is expected to evolve.
...Southern Upper Great Lakes vicinity southwestward to Texas...
While weak capping should prevail across the southern Plains today,
mixing in the vicinity of a weak dryline over central Texas could
allow an isolated storm or two to develop, and possibly persist into
the evening. Given steep lapse rates aloft and deep mixed layer,
hail and/or wind exceeding severe levels could occur, in this highly
More likely development of showers and thunderstorms is expected
along the surface baroclinic zone that extends northward into the
Upper Great Lakes region, perhaps beginning late this afternoon
across northern portions of the risk area and then expanding
southward along the cold front with time. With moderately strong
flow aloft atop the frontal zone across northern portions of the
risk area, a couple of stronger/rotating storms may evolve. Though
hail is expected to be the main risk given steep mid-level lapse
rates, a locally strong gust or two, or brief tornado, would also be
possible if a sustained, rotating storm can develop.
As storms develop south-southwestward into the evening and
overnight, into a region of weaker shear but steep lapse rates,
potential for hail with a few of the strongest storms is expected.
At this time, any focused areas for greater severe potential remain
difficult to discern, and thus will maintain the broad MRGL risk
area this forecast.
...Lower Mississippi Valley vicinity...
Weak QG ascent is forecast to spread into Louisiana and adjacent
Mississippi this afternoon and into this evening, as somewhat
ill-defined/weak cyclonic disturbances in the southern-stream flow
move across northern Mexico and Texas this morning, and begin
affecting the Lower Mississippi Valley area. A gradual increase in
convection through the afternoon is expected, as weak
destabilization of the moist boundary layer occurs. Some increase
in mid-level west-southwesterly flow with time will occur across
this area, as the upper disturbance(s) approach, providing ample
shear for a few stronger storms to potentially evolve. Hail would
likely remain the primary severe risk with one or two of the
strongest storms, though a stronger wind gust or even a brief
tornado cannot be ruled out given weakly veering flow with height,
and the moist boundary layer supporting surface-based updrafts.
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