SPC AC 070600

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0100 AM CDT Wed Apr 07 2021

   Valid 071200Z - 081200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   SOUTHEAST ARKANSAS...NORTHWEST MISSISSIPPI AND NORTHERN LOUISIANA...

   ...SUMMARY...
   Scattered severe thunderstorms are expected from this afternoon into
   the evening across parts of the lower Mississippi Valley, Arklatex
   and Ozarks. Wind damage, hail and a few tornadoes will be possible.
   Other isolated severe storms may develop in the mid Mississippi and
   lower Missouri Valleys.

   ...Lower Mississippi Valley/Arklatex/Ozarks...
   An upper-level low will move across the central Plains today as a 60
   to 75 kt mid-level jet rounds the base of the system. At the
   surface, a low is forecast to move across the mid Missouri Valley as
   a cold front advances quickly eastward across the central and
   southern Plains. Ahead of the front, a corridor of instability is
   forecast to develop by midday across western Missouri. The
   instability combined with lift associated with the nose of a 40 to
   50 kt low-level jet will likely contribute to thunderstorm
   development. A north-to-south band of strong thunderstorms is
   forecast to move eastward across central and northern Missouri
   during the early afternoon. A wind-damage threat may develop with
   this band.

   Further to the south, moderate instability is forecast to develop by
   early afternoon across much of east Texas, Arkansas and Louisiana.
   The axis of the low-level jet will be located across central
   Arkansas, where thunderstorm development should take place during
   the early afternoon. A band of large-scale ascent is forecast to
   move eastward into the Arklatex. This should result in a gradual
   expansion of convective coverage from central Arkansas southward
   into northern Louisiana during the mid afternoon. Forecast soundings
   at 21Z along this corridor from Little Rock, Arkansas southward to
   Monroe, Louisiana increase surface dewpoints in the mid to upper 60s
   F and have MLCAPE peaking in the 1500 to 2000 J/kg range. Strong
   deep-layer shear is forecast with 0-3 km storm-relative helicities
   increasing to between 400 and 500 m2/s2. This should be favorable
   for supercells associated with a threat for tornadoes and wind
   damage. The potential for tornadoes will be greatest during the late
   afternoon as the low-level jet and mid-level jet become juxtaposed
   across the lower Mississippi Valley. As storm coverage expands, a
   line of severe storms, associated with wind damage, is expected to
   move into western Mississippi.

   ...Lower Missouri Valley...
   An upper-level low will move across the central Plains today. At the
   surface, a low will move into the mid Missouri Valley. Ahead of the
   low, a moist axis should be in place from northern Missouri into
   central Iowa. Surface dewpoints in the mid to upper 50s F will
   contribute to destabilization by late morning. Thunderstorm
   development is expected to take place ahead of a band of large-scale
   ascent. This band is forecast to move northeastward across
   northeastern Missouri and southern Iowa during the afternoon. MLCAPE
   around 1000 J/kg along with moderate deep-layer shear may be enough
   for a marginal severe threat. The primary threat will be for
   marginally severe wind gusts, associated with multicell line
   segments.

   ..Broyles/Wendt.. 04/07/2021

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