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...

   ...SUMMARY...
   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.

   ...Synopsis...
   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
   conditional scenario.

   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.

   ..Goss/Broyles.. 03/04/2024

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