Dec 30, 2020 0600 UTC Day 1 Convective Outlook
Updated: Wed Dec 30 05:27:40 UTC 2020 (20201230 1200Z Day 1 shapefile | 20201230 1200Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20201230 1200 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MARGINAL 35,295 6,958,456 Houston, TX...Austin, TX...Corpus Christi, TX...College Station, TX...Sugar Land, TX...
Probabilistic Tornado Graphic
20201230 1200 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
2 % 17,628 2,820,811 Corpus Christi, TX...Sugar Land, TX...Missouri City, TX...Victoria, TX...Mission Bend, TX...
Probabilistic Damaging Wind Graphic
20201230 1200 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
5 % 17,628 2,817,842 Corpus Christi, TX...Sugar Land, TX...Missouri City, TX...Victoria, TX...Mission Bend, TX...
Probabilistic Large Hail Graphic
20201230 1200 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
5 % 35,246 6,876,476 Houston, TX...Austin, TX...Corpus Christi, TX...College Station, TX...Sugar Land, TX...
   SPC AC 300527

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1127 PM CST Tue Dec 29 2020

   Valid 301200Z - 311200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE LOWER AND MIDDLE TEXAS COASTAL PLAIN VICINITY THIS AFTERNOON
   INTO TONIGHT...

   ...SUMMARY...
   Thunderstorms -- and limited severe potential -- will affect
   portions of the Texas Coastal Plain and Hill Country this afternoon
   into the overnight hours.

   ...Synopsis...

   A progressive but split flow regime is in place over the CONUS
   today. An upper shortwave trough over the Upper Midwest will shift
   eastward across the Great Lakes to the Northeast. Meanwhile, in the
   southern stream, an upper shortwave trough over northwest Mexico and
   the southern Rockies will develop an upper low over northern Mexico,
   and pivot eastward toward the Rio Grande in TX by Thursday morning.
   Another shortwave trough will move over the Pacific Northwest
   overnight, and could bring isolated thunderstorms to the WA/OR
   coast. 

   ...Middle and Lower TX Coastal Plain vicinity...

   A southeastward-advancing cold front will extend from northwest AR
   into southeast OK and towards the Edwards Plateau of TX. Low level
   southerly flow will continue to transport Gulf moisture northward
   ahead of the front. Instability will be limited however, due to
   ongoing showers and thunderstorms and general cloudiness precluding
   stronger insolation ahead of the front. Additionally, a warm layer
   is evident around 700 mb in most forecast guidance and point
   forecast soundings. This warm layer is also evident in 00z RAOBs.
   While cooling aloft will occur, it likely will be ill-timed with
   frontal passage. As a result, this should act to limit updraft
   intensity. Nevertheless, strong shear will be in place, an a couple
   of storms capable of marginally severe hail are possible across
   parts of the Edwards Plateau to the middle and lower TX coast. 

   During the evening and overnight hours, a surface low will develop
   east/northeast along the lower and middle TX coast. As this occurs,
   low level winds will become more southeasterly, resulting in
   favorably curved low-level hodographs supporting rotating storms.
   This threat should remain confined closer to the coast and just
   ahead of the cold front. While instability will remain limited,
   favorable low-level and bulk shear could result in a couple of
   storms capable of producing a tornado or locally damaging wind
   gusts.

   ..Leitman.. 12/30/2020

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