NWS Storm Prediction Center - Day 1 Convective Outlook

Nov 29, 2022 2000 UTC Day 1 Convective Outlook
Updated: Tue Nov 29 19:59:53 UTC 2022
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Overview Overview

 Forecast Discussion - Day 1 Convective Outlook


   SPC AC 291959

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0159 PM CST Tue Nov 29 2022

   Valid 292000Z - 301200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
   AND TONIGHT OVER PARTS OF NORTHEAST LOUISIANA...EXTREME SOUTHEAST
   ARKANSAS...CENTRAL AND NORTHERN MISSISSIPPI...AND NORTHWEST
   ALABAMA...

   ...SUMMARY...
   Strong tornadoes, very large hail, and severe wind gusts are
   forecast this afternoon into the overnight period across parts of
   the lower to mid Mississippi Valley, Mid-South and parts of the
   Southeast.

   ...20Z Update...
   A regional tornado outbreak still appears possible from northern LA
   into central/northern MS and potentially into western AL. Rich
   low-level moisture has streamed northward with the aid of a strong
   low-level jet, as steep midlevel lapse rates (greater than 8 C/km on
   12Z SHV sounding) have overspread the region from the west. MLCAPE
   has increased into the 1500-2000 J/kg range across the warm sector,
   and storms are gradually increasing in coverage and intensity across
   parts of LA/MS. Strong and favorably veered wind profiles will
   support several long-lived supercells late this afternoon into this
   evening. With relatively weak low-level lapse rates, it may take
   some time for storms to become tornadic, but a few long-track strong
   tornadoes will be possible late this afternoon into tonight as
   supercells mature and move northeastward. 

   The primary change at 20Z is to expand the Marginal Risk slightly
   eastward across a larger portion of western GA, southeast AL, and FL
   Panhandle. This change was made to account for the possibility of
   nocturnal storms reaching these areas prior to the end of the
   forecast period at 12Z.

   ..Dean.. 11/29/2022

   .PREV DISCUSSION... /ISSUED 1021 AM CST Tue Nov 29 2022/

   ...Regional Outbreak of severe thunderstorms and tornadoes is
   forecast today and tonight for parts of the lower Mississippi
   Valley...

   ...Lower MS Valley...
   Morning water vapor imagery shows a broad upper trough over much of
   the CONUS this morning, with several fast moving shortwave troughs
   moving across the southwest into the southern Plains.  Strong
   southerly low-level winds have developed across the lower MS Valley,
   aiding in the rapid return of rich Gulf moisture.  Dewpoints in the
   mid/upper 60s have spread into much of east TX and LA, and should
   extend into central MS by mid-afternoon.  Plentiful low clouds are
   present, limiting daytime heating.  But relatively steep mid-level
   lapse rates and returning moisture will lead to widespread MLCAPE
   values of 1000-1500 J/kg later today, with only a weak cap.

   Vertical shear profiles are very strong throughout the region, with 
   effective SRH values of 200-400 m2/s2 beneath 50+ knots of
   deep-layer shear.  Given the subtle forcing today, relatively
   long-lived discrete supercell storms are expected with an attendant
   threat of intense and long-track tornadoes.

   Present indications are that primary thunderstorm development will
   begin early this afternoon over parts of LA, spreading quickly into
   MS.  This corridor may see multiple waves of severe convection as
   storms redevelop upstream through the evening.  Along with the
   strong tornado threat, very large hail and damaging wind gusts may
   occur with these storms.  Consideration was made to introduce a
   small HIGH risk, but still too much uncertainty in the exact
   corridor of highest risk since moisture is not yet in place and
   there is no surface boundary to focus on.

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z



Data courtesy the Storm Prediction Center
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