ZCZC SPCSWOD48 ALL
   ACUS48 KWNS 170917
   SPC AC 170917

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0417 AM CDT Thu Mar 17 2022

   Valid 201200Z - 251200Z

   ...DISCUSSION...
   Models continue to depict likelihood for a multi-day -- and
   potentially widespread -- severe weather episode across the
   south-central and southeastern U.S. through the first part of next
   week.  Deterministic global models, as well as both GEFS and ECMWF
   ensemble means, are in good agreement with pattern evolution through
   Day 6 and into Day 7, lending confidence to the evolving scenario.

   Day 4/Sunday, a digging upper trough will shift across the western
   U.S., with a closed low expected to evolve over New Mexico vicinity
   overnight.  Low-level moisture will be returning into the southern
   Plains at this point, but in an incomplete manner, and thus any risk
   for severe weather late Sunday night/Monday morning should remain
   rather low, and likely confined primarily to hail with elevated
   overnight storms.

   By Day 5/Monday, as the upper low moves northeastward across New
   Mexico toward the High Plains, a surface low is forecast to evolve
   over western Texas, and move toward western Oklahoma.  As this
   occurs, continued advection of high theta-e Gulf air into roughly
   the eastern half of Texas will occur ahead of an advancing cold
   front.  As the airmass diurnally destabilizes, an increase in storm
   coverage an intensity is expected.  With very strong
   southwesterly/south-southwesterly flow aloft, atop
   south-southeasterlies at low levels, deep-layer shear will favor
   supercells, along with sufficient low-level shear to support
   potential for tornadoes -- a few possibly strong.  Large hail and
   damaging winds are also expected.

   As the upper system makes only slow eastward progress Day 6/Tuesday,
   another day of severe weather is expected, displaced somewhat to the
   east as the surface front progresses.  Continued influx of Gulf
   moisture into the warm sector will permit ample CAPE to develop,
   while strong low-level and deep-layer shear will again be present
   across the warm sector.  This will again favor an all-hazards severe
   event, including tornado potential, that will continue through the
   evening and into the overnight period.

   The severe-weather risk will likely continue into Wednesday/Day 7,
   as a portion of the larger-scale upper trough ejects northeastward
   across the Mid South and Ohio Valley.  With forcing/large-scale
   ascent likely to become somewhat displaced from the more favorably
   moist/unstable airmass to the south, severe potential may be
   slightly less than prior days.  Still, with favorable shear across a
   moist pre-frontal airmass from the southern Appalachians southward,
   severe storms are expected once again.

   By Thursday, models begin to deviate in terms of both upper-level
   and surface pattern evolution, and thus any convective/severe risk
   across Florida and adjacent areas appears difficult to quantify due
   to predictability issues.

   ..Goss.. 03/17/2022

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