SPC AC 091730

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1230 PM CDT Fri Apr 09 2021

   Valid 101200Z - 111200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER A PORTION
   OF THE GULF COAST STATES...

   ...SUMMARY...
   Scattered severe thunderstorms are expected from southeast Louisiana
   eastward to the Florida Panhandle, and northward into Alabama and
   western Georgia Saturday. Damaging wind appears to be the main
   threat, but isolated tornadoes are also possible.

   ...Synopsis...

   Within a broad synoptic upper trough a shortwave trough will move
   from the middle MS Valley early Saturday into the OH Valley later in
   the afternoon. A low-amplitude southern-stream shortwave trough will
   move along the Gulf Coast then northeast into the Carolinas by late
   afternoon and evening. By 12Z Saturday a cold front will extend from
   a low near St. Louis southwestward into the lower MS Valley and
   southeast TX. A warm front will extend southeast from the surface
   low through the TN Valley and Southeast States. The surface low will
   lift northward to near the Chicago area by late afternoon while the
   cold front continues east through the OH/TN Valleys and into the
   southeast States. By early evening the warm front should extend from
   the surface low southeast through the OH Valley and into the Middle
   Atlantic area. 

   ...Gulf Coast States...

   It is likely that storms will have consolidated into an organized
   squall line by 12Z Saturday with embedded mesovortices and bowing
   structures. A few discrete supercells may also be ongoing ahead of
   the line. These storms will be embedded within strong deep-layer
   winds and accompanying intense (60+ kt) low-level jet associated
   with the southern-stream shortwave trough. Effective bulk shear from
   40-50 kt and large 0-1 km hodographs will support the potential for
   scattered damaging wind and isolated significant wind damage as well
   as a few tornadoes, as storms advance east through the moist and
   moderately unstable warm sector across southern portions of the Gulf
   Coast states during the day. 

   ...Carolinas into a portion of the Middle Atlantic...

   The advection of upper 50s to low 60s F dewpoints and pockets of
   diabatic heating should contribute to marginal instability during
   the day in this region. Both low and mid-level winds will increase
   with the approach of the shortwave trough with effective bulk shear
   increasing to 35-45 kt. Scattered thunderstorms are expected to
   develop during the day as the surface layer destabilizes. Potential
   will exist for some of the storms to organize including possibility
   of a few supercells and bowing segments. Threat will exist for
   isolated damaging wind with a more conditional threat for a couple
   of tornadoes. Have introduced a MRGL risk for this update, but a
   SLGT risk may be required for a portion of this area in day 1
   outlooks if confidence increases that instability will become
   sufficient for a more robust threat.  

   ...Midwest...

   Some destabilization is expected along warm front extending east of
   surface low during the afternoon across northern IL. If sufficient
   surface heating occurs, a few robust updrafts may develop along this
   boundary where potential will exist for a few low-topped supercells
   capable of brief, isolated tornadoes.

   ...OH Valley...

   Forced bands of convection will spread northeast during the day
   along the warm conveyor belt. Activity will be embedded within
   moderate to strong deep-layer flow but weak instability. A few
   locally strong gusts could accompany some of this activity.

   ..Dial.. 04/09/2021

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