SPC AC 290112

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0812 PM CDT Sun Apr 28 2024

   Valid 290100Z - 291200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PART OF
   EAST TEXAS...WESTERN TO NORTHERN LOUISIANA...AND SOUTHERN
   ARKANSAS...

   ...SUMMARY...
   Severe storms, capable of wind damage, a couple tornadoes and
   isolated large hail are likely this evening across parts of east
   Texas, northern/central Louisiana and southern Arkansas. A few
   severe storms, associated with wind damage and hail will also be
   possible in a broader area from the southern Plains and Lower
   Mississippi Valley northward to the Ozarks and Lower Missouri
   Valley.

   ...Sabine River Valley/Ark-La-Tex/Southern Plains/Ozarks...
   The latest water vapor imagery shows a mid-level trough over the
   southern Plains, with southwesterly flow over the Ark-Latex and
   lower Mississippi Valley. A shortwave trough, and an associated 50
   to 60 knot mid-level jet, appear to be moving through the
   Ark-La-Tex. A large cluster of strong to severe storms is ongoing
   near this shortwave trough, and to the east of the jet streak, from
   east Texas into far northwest Louisiana. This cluster is expected to
   move eastward across the remainder of east Texas, and into northern
   and western Louisiana this evening, where linear MCS development
   will be possible.

   The latest surface analysis shows the moist sector, with backed
   southeasterly flow, across the Sabine and Lower Mississippi Valleys.
   A mesolow is located in the Ark-La-Tex. Surface dewpoints across the
   moist sector are in the mid to upper 60s F, with the RAP/observed
   RAOBS estimating MLCAPE generally in the 1500 to 2000 J/kg range.
   The instability will sustain a large cluster of storms, as it moves
   toward the Mississippi Valley this evening. In addition, regional
   WSR-88D VWPs at Fort Polk and Shreveport, Louisiana have 0-6 km
   shear around 40 knots, with a lot directional shear from the surface
   to 4 km above ground level. This will continue to be favorable for a
   severe bowing line segment for several more hours this evening. Wind
   damage will be likely along the leading edge of the line. If a cold
   pool can become organized, then the wind damage threat could become
   more widespread. The Fort Polk, Louisiana WSR-88D VWP also has 0-3
   km storm-relative helicity around 225 m2/s2 suggesting a tornado
   threat will exist with the line, and with the more intense cells
   further to the southwest. The more intense semi-discrete storms in
   east Texas should be supercellular, having a large hail and isolated
   tornado threat. The severe threat is expected to continue for
   several more hours, but should become marginal in the late evening
   and overnight period. A severe threat will also be possible further
   to the north into the Ozarks and lower Missouri Valley, but should
   be isolated due to the airmass largely being overturned.

   Further to the north and west into central and eastern Oklahoma,
   north-central Texas, RAP analysis show moderate instability in
   place, with MLCAPE generally from the 1000 to 2000 J/kg. In
   addition, the observed sounding at Oklahoma City, and forecast
   soundings further to the east have 0-6 km shear generally in the 30
   to 45 knot range. This, combined with steep mid-level lapse rates
   should support a severe threat early this evening. Hail and isolated
   strong wind gusts will be the primary threats. Large-scale
   subsidence behind the exiting shortwave trough should keep any
   severe threat marginal this evening.

   ..Broyles.. 04/29/2024

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