Dec 20, 2021 1300 UTC Day 1 Convective Outlook
Updated: Mon Dec 20 12:37:20 UTC 2021 (20211220 1300Z Day 1 shapefile | 20211220 1300Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20211220 1300 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Tornado Graphic
20211220 1300 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Day 1 Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Damaging Wind Graphic
20211220 1300 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Day 1 Wind Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Large Hail Graphic
20211220 1300 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Day 1 Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
   SPC AC 201237

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0637 AM CST Mon Dec 20 2021

   Valid 201300Z - 211200Z

   ...NO SEVERE THUNDERSTORM AREAS FORECAST...

   ...SUMMARY...
   The risk of severe thunderstorms appears negligible across the U.S.
   Monday through Monday night.

   ...Synopsis...
   Southern-stream shortwave trough currently moving across Texas is
   forecast to continue progressing eastward, reaching the Lower MS
   Valley by late tonight/early Tuesday morning. However, recent
   surface analysis places the cold front well offshore in the Gulf of
   Mexico, limiting low-level moisture and buoyancy ahead of the
   shortwave and precluding thunderstorms across Texas and the
   Southeast States. Isolated thunderstorms are possible along the
   eastern Florida Coast as the low-level winds gradually become more
   westerly throughout the evening in response to the approaching
   shortwave trough and attendant surface low. Isolated thunderstorms
   are possible across south Florida as well. 

   The northern stream will remain fairly progressive, with one
   shortwave trough moving across Ontario and Quebec throughout the day
   while another following in its wake moves across Alberta,
   Saskatchewan, and Montana. A strong upper low will make slow
   eastward progress across the northwest Pacific Ocean toward the
   Pacific Northwest/northern CA, but will still remain well offshore
   early Tuesday. Stable conditions will prevent thunderstorms in any
   area of the CONUS besides Florida.

   ..Mosier.. 12/20/2021

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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z