SPC AC 110548

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1148 PM CST Fri Dec 10 2021

   Valid 111200Z - 121200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE OHIO
   VALLEY TO THE NORTHERN GULF STATES...

   ...SUMMARY...
   Isolated strong to severe thunderstorms remain possible from the
   Ohio/Tennessee Valleys into the northern Gulf States. Damaging wind
   gusts and perhaps a tornado will be possible, mainly early in the
   day. Isolated strong wind gusts cannot be ruled out over parts of
   the Mid Atlantic during the evening.

   ...Ohio Valley to northern Gulf States...

   Very dynamic and progressive trough is shifting across the MS Valley
   late this evening. This feature will move into the Great Lakes/OH
   Valley by 18z, arcing southwest into AR where mid-level flow will be
   decidedly westerly and considerably weaker (50-80kt) than across the
   OH Valley (120kt). 210-270m mid-level height falls will spread
   across the Great Lakes into southeast Canada ahead of the trough and
   this will encourage strong/severe frontal convection despite poor
   lapse rates/weak buoyancy north of the OH River. Organized
   convection should be ongoing at the beginning of the period along
   the front from western OH-KY-middle TN-northern MS-LA. This band of
   frontal convection may be severe at the beginning of the period as
   low-level moisture has advanced across southern IN into southwestern
   OH at 0530z where surface dew points are now in the lower 60s. NAM
   forecast sounding for LUK at 13z just ahead of the front depicts
   very strong shear with poor lapse rates and SBCAPE on the order of
   600 J/kg. While much of this activity may be QLCS in nature, a few
   supercells cannot be ruled out. Damaging winds are possible with
   this early-day frontal convection along with some threat for
   embedded tornadoes.

   Farther south across the TN Valley into the central Gulf States,
   surface heating should remain limited ahead of the trailing cold
   front. Latest model guidance continues to suggest the boundary will
   be convectively active at sunrise and despite poor lapse rates and
   warmer mid-level temperatures, dew points have risen into the upper
   60s to near 70F. Strong shear will likely maintain the frontal
   squall line as it advances across the weak-buoyancy air mass.
   Damaging winds and perhaps a tornado or two are the primary threats.

   ...Mid Atlantic...

   Modified boundary-layer air mass will return across the Mid Atlantic
   this morning and this will aid weak destabilization as far north as
   southeast PA as mid-level profiles cool and inhibition weakens. Even
   so, air mass will struggle to destabilize with forecast soundings
   suggesting MUCAPE perhaps as high as 300 J/kg by early evening.
   Forced line of convection may generate locally damaging winds but
   this activity should remain isolated due to poor lapse rates and
   weak buoyancy.

   ..Darrow/Squitieri.. 12/11/2021

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z