SPC AC 091948

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0248 PM CDT Thu May 09 2024

   Valid 092000Z - 101200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM CENTRAL
   TEXAS EAST ACROSS PARTS OF THE CENTRAL GULF COAST STATES AND
   SOUTHERN GEORGIA...

   ...SUMMARY...
   Very large hail with multiple supercells appears probable across
   parts of north and central Texas into the ArkLaTex vicinity this
   afternoon and evening.  A broader corridor of severe hail and
   damaging-wind potential will extend from east Texas into the lower
   Mississippi Valley and Southeast.

   ...Southeast...

   The main changes with the 20z update were to remove most severe
   probabilities from much of SC/NC. Convection has mostly moved
   offshore and redevelopment is not expected. Furthermore, instability
   will remain very weak across much of NC and any storms that may form
   into the evening/overnight should remain fairly weak. Probabilities
   were not changed much over AL/GA from the previous outlook given
   expected MCS moving into these areas overnight and posing a risk for
   damaging wind gusts. 

   ...OK/TX to Lower MS Valley...

   The Marginal risk (level 1 of 5) was extended northward into central
   OK where ongoing thunderstorms will pose some risk for marginally
   severe hail this afternoon/evening with eastward extent into AR. 

   The Enhanced risk (level 3 of 5) has been nudged a small amount
   south across southeast TX and LA based on latest short term guidance
   and CAMs trends. Damaging gusts and hail will be the main concern as
   thunderstorms congeal over north/central TX into an eastward
   progressing MCS during the evening/overnight.

   ..Leitman.. 05/09/2024

   .PREV DISCUSSION... /ISSUED 1146 AM CDT Thu May 09 2024/

   ...Synopsis...
   Water-vapor imagery late this morning shows a mid-level trough over
   the western Great Lakes/Upper MS Valley and a mid- to upper-level
   low situated over eastern UT.  A broad belt of strong westerly
   500-mb flow will extend from the Desert Southwest eastward across
   the southern Great Plains and to the Mid-Atlantic and Southeast U.S.
   coast.  Satellite imagery also depicts an embedded disturbance
   quickly moving east across AL into western GA late this morning. 
   Another upstream disturbance is currently moving east-northeast
   across northern Mexico into the Rio Grande Valley/Edwards Plateau
   late this morning.  In the low levels, a surface low over the OH
   Valley is largely displaced from the area of greatest severe
   thunderstorm concern today, which is located from TX east to the
   GA/SC vicinity.  A myriad of ongoing thunderstorm bands and
   convective outflow over the Southeast will serve as corridors for
   additional and continued thunderstorm activity through at least the
   early to mid afternoon.  Farther west, a dryline and west-east
   oriented frontal zone over north TX east to the ArkLaMiss will also
   act to focus severe thunderstorm development later today and
   tonight.

   ...North, central and east TX...
   Scattered thunderstorms are forecast to develop this afternoon and
   evening ahead of the aforementioned mid-level disturbance across
   central and eventually into eastern portions of TX.  Storm
   development will likely initially favor near and north of a frontal
   zone draped across north TX with dryline storms later this
   afternoon.  The Fort Worth and Del Rio, TX raobs sampled 8-9 deg
   C/km 700-500 mb lapse rates.  Very large CAPE via a very moist
   boundary layer will likely favor explosive updraft growth as storms
   quickly become supercellular.  Low-level shear will likely be
   subdued due to lack of a strong low-level mass response, thereby
   acting to limit overall tornado potential.  Nonetheless, a few
   supercells within an environment characterized by very large
   buoyancy and moist low levels will potentially yield some tornado
   risk via local storm-scale processes such as mergers and boundary
   interactions.  Large to giant hail --potentially 3+ inches in
   diameter -- as well as locally severe gusts and perhaps a tornado or
   two will be the primary threats.  The wind threat could evolve
   upscale and start forward-propagating eastward into LA wherever
   early cells can aggregate into clusters.  QLCS tornadoes are also
   possible with any MCS.

   ...Southeast...
   Bands of strong to severe thunderstorms ongoing during the midday
   will likely continue to propagate east-southeast across eastern AL
   into GA and SC.  A very moist/unstable airmass evident in the 12z
   Birmingham and Atlanta raobs (1800 and 1300 J/kg MLCAPE) will
   continue to gradually destabilize, despite considerable cloud
   coverage across AL/GA.  Fewer clouds across south-central GA into
   the coastal plain of SC will continue to heat more rapidly
   downstream of the ongoing storms and yield an environment favorable
   for a continued damaging-wind risk through the mid to late
   afternoon.  For short-term convective details and environmental
   analysis, please refer to MCD #728 and forthcoming MCDs over the
   region.

   Farther west, from western AL westward into LA this afternoon, weak
   large-scale subsidence in wake of the AL/GA impulse will probably
   act to limit storm coverage during the day.  Isolated severe storms
   are possible as the airmass continues to destabilize and potentially
   yield an isolated hail/wind threat.  Later this evening into the
   overnight, a cluster of thunderstorms is forecast to evolve over the
   Arklatex and move east across LA into MS and eventually MS/AL/FL
   Panhandle.  Severe gusts (60-85 mph) and the risk for a few
   tornadoes will probably accompany this activity as it moves east
   during the evening and overnight.

   ...Mid/upper Ohio Valley to Tidewater...
   Isolated to widely scattered thunderstorms are possible this
   afternoon across portions of the OH Valley, with damaging gusts and
   marginally severe hail possible.  Some heating coupled with lower
   60s surface dewpoints will contribute to MLCAPE ranging from
   500-1500 J/kg.  Though upper flow will be strong, nearly
   unidirectional profiles and lack of greater midlevel winds should
   keep effective-shear magnitudes in the 30-40 kt range over much of
   the area.

   Farther east/southeast, cool/stable air north of a damming/preceding
   frontal zone across VA and the Delmarva should limit the northern
   end of severe potential.  Destabilization and available moisture
   will be substantially limited today in the nominal warm sector,
   between the damming front and a great deal of MCS/outflow activity
   to the south over the Carolinas/GA.  Therefore, while thunderstorms
   are possible this afternoon and deep shear may be adequate for a few
   organized cells, severe potential appears isolated.

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