SPC AC 051248

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0648 AM CST Sun Jan 05 2025

   Valid 051300Z - 061200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE LOWER MISSISSIPPI VALLEY...

   ...SUMMARY...
   Severe thunderstorms are expected this afternoon and evening from
   the Sabine River Valley into the Mid-South and lower Mississippi
   Valley. Tornadoes and scattered severe/damaging winds should be the
   primary threats. A couple of strong tornadoes may also occur.

   ...East Texas into the Mid-South and Lower Mississippi Valley...
   A strong shortwave trough over the central/southern High Plains this
   morning will evolve into a closed upper low later today over eastern
   KS/western MO. Related mid-level height falls and large-scale ascent
   will encourage the primary surface low over central OK to develop
   eastward to the Mid-South vicinity by late afternoon/early evening.
   An attendant cold front will continue to sweep east-southeastward
   over the southern Plains and lower MS Valley/Southeast through
   tonight. Pronounced low-level mass response, with a 45-60 kt
   low-level jet, will aid in the northward transport of partially
   modified Gulf moisture across east TX and the lower MS Valley ahead
   of the surging cold front.

   Even though low/mid-level lapse rates are forecast to generally
   remain modest, low to mid 60s surface dewpoints should be present by
   early afternoon in a narrow corridor along and just ahead of the
   cold front from parts of east TX to northern MS and vicinity.
   Filtered daytime heating should support around 500-1000 J/kg of
   MLCAPE by mid afternoon, with weaker instability with northward
   extent into western TN near the surface low. Ample deep-layer shear
   (40-50 kt) will be present across the warm sector to support
   organized severe convection, including the potential for some
   supercells. Current expectations are for surface-based convection to
   develop and corresponding severe threat to increase in the early to
   mid afternoon as the boundary layer gradually destabilizes. Given
   the forcing of the cold front itself, a line of convection is
   expected to eventually consolidate and pose a threat for mainly
   scattered severe/damaging winds and a few tornadoes as it moves
   quickly eastward through the early evening.

   However, most high-resolution guidance shows some chance for
   thunderstorms to develop along a weak surface trough/confluence zone
   ahead of the front early this afternoon from parts of
   central/northern LA into western MS. The strong low-level jet will
   support enhanced low-level shear (effective SRH around 200-350+
   m2/s2), and a threat for tornadoes with any supercells that can
   mature in the narrow warm sector ahead of the surging cold front.
   Given the rather favorable shear and enlarged low-level hodographs
   shown in 06Z NAM/11Z RAP forecast soundings, a couple of strong
   (EF-2) tornadoes appear possible with any sustained supercell across
   this region. The best time frame for this tornado potential should
   be mainly around 19-23Z, before any pre-frontal convection becomes
   absorbed within the line. Isolated hail may also occur with this
   activity. Embedded/QLCS tornadoes and damaging winds will still
   remain possible for as long as the line can remain surface based.
   Severe potential should quickly diminish with the line late this
   evening and overnight as it continues into AL and encounters a less
   favorable thermodynamic environment.

   ..Gleason/Bentley.. 01/05/2025

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