SPC AC 151729

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1229 PM CDT Mon Mar 15 2021

   Valid 161200Z - 171200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   THE SOUTHERN/CENTRAL PLAINS TUESDAY NIGHT INTO EARLY WEDNESDAY
   MORNING...

   ...SUMMARY...
   Isolated severe thunderstorms are possible from the lower
   Mississippi Valley through the central Gulf Coast states through the
   afternoon and early evening on Tuesday. Strong wind gusts, hail and
   a tornado or two are possible with this activity. 

   Additional severe storms are expected across parts of Texas,
   Oklahoma and Kansas late Tuesday night into early Wednesday morning.
   Large hail will be the main hazards with this activity, though
   strong gusts and a tornado can not be ruled out.

   ...Synopsis...

   A broad swath of moderate deep-layer southwesterly flow will extend
   from the southern Plains to the TN and OH Valley vicinities, ahead
   of a compact upper low ejecting eastward from the lower CO Valley to
   the southern Plains. Strong capping across the southern Plains will
   limit thunderstorm potential until the evening/overnight hours
   across the southern Plains. Further east, thunderstorms will be
   ongoing across parts of the lower MS Valley into GA in a warm
   advection regime. 

   ...Southern Plains to Ozarks vicinity...

   A midlevel ridge will reside across the region through the
   afternoon. This will maintain a capping inversion and limit
   convection through the first half of the period. By evening, the
   upper low/shortwave trough will eject eastward, resulting in falling
   heights and cooling aloft. Southerly low level flow will transport
   Gulf moisture northward ahead of a developing surface low over the
   southern High Plains. Upper 50s to low 60s F dewpoints will spread
   across much of central and northern TX and into the eastern
   two-thirds of OK and much of AR, with lower values sneaking into
   southeast KS and southern MO after 00z. As the surface low
   progresses eastward, a Pacific front/dryline will spread across
   western OK/TX, and become oriented roughly along/to the east of the
   I-35 corridor in OK/TX by 12z Wednesday. 

   After 00z, and more likely after 06z, increasing moisture beneath
   very steep midlevel lapse rates amid strong ascent and favorable
   deep layer wind profiles will mainly support large hail potential.
   This potential will extend along the eastward-advancing cold front
   across western/central TX, in storm clusters developing near the
   surface low, and along a west-east oriented warm front near the
   OK/KS border into northwest AR. Convection will likely remain
   somewhat elevated along the cold front given timing during the
   overnight hours, and storm motion vectors that could favor
   undercutting by the front. However, strong low level shear and
   enlarged low level hodographs will support rotating cells,
   especially in the vicinity of the warm front. Should a storm become
   rooted in the boundary layer on the warm side of the front, a
   tornado or damaging wind gusts can not be ruled out. 

   ...Central Gulf Coast States...

   Isolated thunderstorms will likely be ongoing at the start of the
   period across portions of the lower Mississippi Valley/central Gulf
   Coast region, in an area of persistent low-level warm advection/weak
   ascent.  With time, a backdoor front over Georgia, and the weakening
   Pacific cool front crossing the central Gulf Coast region, will
   loosely consolidate into a west-to-east warm front, that will lift
   slowly northward through the afternoon and evening as the western
   synoptic system ejects into the southern Plains.

   Mid-60s surface dewpoints will reside across much of the region,
   with temperatures warming into the 70s, providing a broad area of
   500-1250 J/kg MLCAPE. Larger-scale forcing will remain weak across
   the region as the upper trough remains well west of the area.
   However, effective shear greater than 35 kt and modest midlevel
   lapse rates will support periodically organized convection.
   South/southwesterly flow beneath 700 mb will remain modest, less
   than 25-30 kt in most cases, but small, curved low level hodographs
   could result in some weakly rotating cells. Periodic clusters of
   storms across this region through afternoon/early evening will
   likely occur, with a few storms possibly becoming transiently
   severe. Locally damaging winds, marginal hail, or even a tornado
   cannot be ruled out. Given the transient threat over a large area, a
   Marginal risk will be maintained.

   ..Leitman.. 03/15/2021

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