SPC AC 311247

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0647 AM CST Mon Jan 31 2022

   Valid 311300Z - 011200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE MIDDLE
   TEXAS COAST AND VICINITY...

   ...SUMMARY...
   A marginal threat for severe hail/wind and perhaps a tornado exists
   this afternoon over the middle Texas Coast and vicinity.

   ...Synopsis...
   In mid/upper levels, troughing will weaken substantially over the
   East Coast and adjoining Atlantic, while a progressive, split-flow
   pattern shifts across the central CONUS.  The split relates to a
   compact, southern-stream cyclone evident in moisture-channel imagery
   over the Permian Basin, Pecos Valley and Llano Estacado of
   southeastern NM and adjoining portions of west TX.  The accompanying
   500-mb low should move southeastward to the JCT/HDO area by 00Z,
   then weaken to an open wave as it moves offshore from the TX Coastal
   Bend tonight.  Meanwhile, a strong surface cold front will cross the
   northern Plains and central High Plains through the overnight hours,
   but will remain well-removed from the area of convective concern. 

   ...TX Coast...
   Elevated convection is ongoing across central TX, with sporadic/
   isolated lightning.  Additional, shallower, low-level convection
   (without lightning for now) is evident mainly east of I-35/I-37
   across the middle TX Coastal Plain, within an early/immature stage
   of low-level return flow from the Gulf.  Convection should become
   more dense and intense across south-central TX through early/mid
   afternoon, as the upper low approaches, with:
   1.  Related DCVA/large-scale ascent increasing over the region from
   west to east and impinging on the western part of...
   2.  A strengthening warm-advection/moisture-transport plume that
   will destabilize the boundary layer in concert with weak,
   cloud-tempered diurnal heating.

   These processes should destabilize the boundary layer modestly,
   amidst weak MLCINH, offsetting weak midlevel lapse rates just enough
   for MLCAPE in the 200-700 J/kg range to develop by mid/late
   afternoon.  This, along with deep lift ahead of the low, will
   contribute to scattered thunderstorms my mid/late afternoon roughly
   between SAT, GLS and CRP, with the most-unstable, surface-based
   inflow parcels along the southern rim of the precip area.  Winds
   will veer favorably with height, beneath strong upper/anvil-level
   flow, and localized/boundary processes may enable brief supercell
   characteristics.  However, weaknesses in midlevel winds will limit
   effective-shear magnitudes to only 20-35 kt over most of the area
   where substantial convection is expected.  Deep shear will be
   stronger farther south across the lower TX Coast and deep south TX;
   however, lack of lift will limit or eliminate convective coverage
   greatly with southwestward extent over those areas.  An arc of
   strong/locally severe thunderstorms may form immediately ahead of
   the low late this afternoon into evening and move offshore, and an
   isolated strong-severe thunderstorms may occur in the precursory
   warm-advection plume.  Lack of greater instability and shear limit
   overall severe potential.

   ..Edwards/Goss.. 01/31/2022

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z