SPC AC 020600

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1200 AM CST Thu Mar 02 2023

   Valid 021200Z - 031200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
   THE ARKLATEX...

   ...SUMMARY...
   A regional severe-thunderstorm outbreak appears likely across parts
   of the southern Plains into the ArkLaTex and ArkLaMiss regions today
   into tonight. Widespread damaging winds, large hail, and tornadoes
   are all expected. A few long-lived, intense tornadoes are possible.

   ...Synopsis...
   A potent mid-level shortwave trough will traverse the southern
   Plains today and approach the lower MS Valley tonight while a
   surface low rapidly intensifies over the Arklatex. Multiple rounds
   of severe thunderstorms are expected through the period, with an
   initial round of storms moving across the Arklatex during the late
   afternoon and a second round moving across the Arklatex into the
   Lower MS Valley during the night. Ahead of the surface low, an
   intensifying low-level jet beneath unseasonably strong mid-level
   flow will promote very strong deep-layer ascent/shear atop rich
   low-level moisture, encouraging significant severe weather in
   association with both rounds of storms. A regional severe
   thunderstorm outbreak is expected, including the potential for
   damaging tornadoes.

   ...Central Texas into the Mid-South - Daytime...
   Showers and thunderstorms should be ongoing at the start of the
   period across eastern TX into southern AR, toward northern AL along
   a diffuse effective warm front, delineating the northward extent of
   the warm sector. As the mid-level trough traverses the southern
   Rockies, rapid surface cyclogenesis should ensue across TX,
   supporting the vigorous northward advection of rich low-level
   moisture into eastern OK/AR. 7-8 C/km mid-level lapse rates will
   overspread upper 60s F surface dewpoints, contributing to 1500-2000
   J/kg MLCAPE across the warm sector. During the day, a 30+ kt
   low-level jet will be situated across the southern Plains,
   overspread by 50+ kt southwesterly mid-level flow, resulting in
   widespread 50-75 kt effective bulk shear across the warm sector.
   Appreciable low-level shear will also be present, with hodographs
   gradually elongating/curving throughout the day. With the mid-level
   trough/300 mb jet streak still lagging to the west, some questions
   remain in terms of how widespread diurnal warm-sector coverage will
   be. Nonetheless, the eastward advance of a merging dryline/pacific
   front will encourage at least isolated supercell storms during the
   afternoon into early evening, with supercells initiating across
   central TX into southeast OK, progressing eastward into the
   Arklatex. Severe gusts, large hail (including 2+ inch stones) and
   tornadoes are all possible. Any supercell that can become sustained
   within the warm sector may produce strong tornadoes.

   ...Arklatex into the Mid-South - Nightime...
   By evening, the mid-level trough will become negatively tilted and
   will accelerate toward the Lower MS Valley, with the surface low
   also expected to undergo rapid intensification. Impressive vertical
   wind profiles will develop as a result of the deep-layer mass
   response to the approaching trough, with a regional but volatile
   severe weather setup taking place. As the Pacific front rapidly
   advances eastward into a buoyant airmass (500-1500 J/kg MLCAPE,
   driven primarily by upper 60s F surface dewpoints), several strong
   to severe storms should initiate along the front. An intense QLCS
   may develop, comprised of a mix of embedded supercells and
   potentially long-lived meso-gamma scale vortices. A 50-60 kt
   low-level jet overspread by 100+ kts of 500 mb flow will support
   very large/curved hodographs amid residual surface-based
   instability. In addition to widespread severe gusts, several
   QLCS/possible embedded supercell tornadoes appear likely with this
   main round of storms. Given the high magnitudes of shear, at least a
   few sustained, strong tornadoes are likely and an intense (EF3+)
   tornado or two cannot be ruled out. One caveat which precludes the
   issuance of higher tornado-driven probabilities this outlook is the
   advection of warm 700 mb temperatures into the low-level jet axis
   during the evening, which may temper low-level updraft stretching
   and in turn, dampen tornado potential with a subset of storms that
   do occur. 

   The QLCS may undergo gradual weakening after crossing the MS river
   around 09Z. Nonetheless, impressive low-level shear profiles and at
   least some surface-based buoyancy (albeit scant) should precede the
   line, with at least some risk of damaging gusts/line-embedded
   tornadoes continuing toward the end of the period.

   ..Squitieri/Darrow.. 03/02/2023

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