Dec 24, 2021 1300 UTC Day 1 Convective Outlook
Updated: Fri Dec 24 12:46:40 UTC 2021 (20211224 1300Z Day 1 shapefile | 20211224 1300Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20211224 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
20211224 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
20211224 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
20211224 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 241246

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0646 AM CST Fri Dec 24 2021

   Valid 241300Z - 251200Z

   ...NO SEVERE THUNDERSTORM AREAS FORECAST...

   ...SUMMARY...
   Isolated thunder is possible over parts of the Pacific Coast States,
   eastern Great Basin and Colorado Plateau.

   ...Synopsis/Discussion...
   Mid/upper-level flow will remain zonal to west-southwesterly over
   most of the CONUS through the period, downstream from a temporarily
   low-amplitude mean trough near the Pacific Coast.  A well-defined,
   southern-stream shortwave trough is apparent in moisture-channel
   imagery offshore from central/southern CA and northern Baja, between
   122W-125W.  This trough will deamplify substantially through the
   period as it moves rapidly inland, reaching the southern Rockies
   around 00Z and parts of IL/IN by 12Z tomorrow.  Associated steep
   low/middle-level lapse rates over the marine layer will support
   isolated thunder potential the next few hours until the trough
   passes over near-coastal southern CA, with isolated thunder also
   possible separately in the central/southern Sierra and adjoining San
   Joaquin Valley.  

   Sufficient low/middle-level moisture and at least marginally deep
   buoyancy to support thunderstorms also is expected over parts of the
   Colorado Plateau and eastern Great Basin.  Some of this activity may
   produce strong gusts, though lack of greater CAPE (MLCAPE generally
   less than 250 J/g) and modest boundary-layer theta-e suggest severe
   potential is too small for an outlook area. An elevated warm-
   advection regime ahead of the weakening trough tonight -- from the
   east-central Plains to the upper Ohio Valley -- will contain a
   60-70-kt west-southwesterly LLJ and modest but increasing moisture
   above the boundary layer.  At this time, buoyancy looks too weak to
   support more than very isolated/rogue lightning, but this regime
   will be monitored for any better-focused thunder potential in
   succeeding outlooks. 

   Meanwhile, a northern-stream perturbation -- now located just
   offshore from WA and Vancouver Island -- will move inland and
   weaken.  Another perturbation will pivot west through south of the
   initial one, with its eastern lobe extending inland over
   northwestern CA/southwestern OR this afternoon and evening. 
   Accompanying cold midlevel temperatures and steep lapse rates over
   the marine layer will support isolated thunder potential with
   convective elements near the coast from northern CA to WA.

   ..Edwards/Gleason.. 12/24/2021

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