Dec 21, 2020 0830 UTC Day 3 Severe Thunderstorm Outlook
Updated: Mon Dec 21 08:08:12 UTC 2020 (20201221 0830Z Day 3 shapefile | 20201221 0830Z Day 3 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20201221 0830 UTC Day 3 Outlook Graphic
Day 3 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MARGINAL 54,056 5,861,545 New Orleans, LA...Baton Rouge, LA...Mobile, AL...Metairie, LA...Lafayette, LA...
Probabilistic Graphic
20201221 0830 UTC Day Probabilitic Graphic
Probability of severe weather within 25 miles of a point.
Hatched Area: 10% or greater probability of significant severe within 25 miles of a point.
Day 3 Prob. Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
5 % 54,061 5,858,418 New Orleans, LA...Baton Rouge, LA...Mobile, AL...Metairie, LA...Lafayette, LA...
   SPC AC 210808

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0208 AM CST Mon Dec 21 2020

   Valid 231200Z - 241200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST
   TEXAS ACROSS THE CENTRAL GULF COAST INTO THE WESTERN FLORIDA
   PANHANDLE...

   ...SUMMARY...
   Isolated severe thunderstorms are possible from southeast Texas
   across the central Gulf Coast into the western Florida Panhandle.

   ...Synopsis...
   A deep surface low is forecast to be centered over east-central
   MN/northwest WI early Wednesday morning. A strong cold front will
   extend southwestward from the low across the Ozark Plateau and into
   north-central TX before arcing more westward through the TX Permian
   Basin. This front is expected to surge southward/southeastward
   throughout the day as the parent surface low moves eastward over the
   Upper Great Lakes and gradually occludes.

   At the same time, upper troughing initially extending from the
   Canadian Prairie Provinces into the central Rockies is expected to
   deepen significantly as it progresses eastward. Additionally,
   mid-level flow surrounding the trough will strengthen. By early
   Thursday morning, a large corridor of 100+kt 500-mb winds is
   expected to extend from the Lower MS Valley through the Upper Great
   Lakes into southeastern Ontario. 

   Modest moisture advection associated with this system will likely
   result in low to mid 60s dewpoints from central/east TX into
   southern AL/MS and the FL Panhandle ahead of surging cold front.
   Widespread cloud cover will temper daytime heating and, along with
   poor lapse rates, will contribute to limited buoyancy. Even so,
   strong vertical shear supports organized storm structures with any
   mature/persistent updrafts. Based on current guidance, highest
   probability of severe storms appears to be across the western FL
   Panhandle early Thursday when the strengthening low-level flow
   aligns with the limited buoyancy.

   ..Mosier.. 12/21/2020

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   NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0830Z