Dec 12, 2021 1300 UTC Day 1 Convective Outlook
Updated: Sun Dec 12 12:41:23 UTC 2021 (20211212 1300Z Day 1 shapefile | 20211212 1300Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20211212 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
20211212 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
20211212 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
20211212 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 121241

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0641 AM CST Sun Dec 12 2021

   Valid 121300Z - 131200Z

   ...NO SEVERE THUNDERSTORM AREAS FORECAST...

   ...SUMMARY...
   A few thunderstorms will be possible across the coastal Pacific
   Northwest through late afternoon.

   ...Synopsis/Discussion...
   In mid/upper levels, a positively tilted synoptic-scale trough will
   move offshore over the Atlantic in the next several hours.  Nearly
   zonal flow will prevail in its wake east of the Rockies, while some
   height falls and backing of mid/upper flow occur over the Pacific
   Coast, in response to amplifying synoptic troughing offshore.  Over
   near-coastal areas of the Pacific Northwest, cooling aloft and steep
   low/middle-level lapse rates will overlie the moist marine boundary
   layer.  This will contribute to essentially uninhibited MLCAPE
   generally under 250 J/kg over land, but extending into icing layers
   suitable for at least isolated lightning generation.  A thunder area
   therefore is maintained over this region.

   At the surface, 11Z analysis showed a cold front extending from
   offshore of the Carolinas southwestward across northern FL, through
   a weak frontal-wave low over the extreme northeastern Gulf, then
   southwestward offshore from the mouth of the Rio Grande.  Some
   convection may accompany or precede this front today as it moves
   southward across parts of the FL Peninsula.  However, this activity
   should remain too shallow for an areal thunderstorm threat, given
   the strong stable layer evident in the last couple RAOB cycles
   between the 700-mb level and the loftier -20C environmental
   isotherm.

   ..Edwards/Leitman.. 12/12/2021

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