Dec 20, 2017 0600 UTC Day 1 Convective Outlook
Updated: Wed Dec 20 05:32:39 UTC 2017 (20171220 1200Z Day 1 shapefile | 20171220 1200Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20171220 1200 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MARGINAL 57,461 9,571,853 Atlanta, GA...Birmingham, AL...Sandy Springs, GA...Tuscaloosa, AL...Roswell, GA...
Probabilistic Tornado Graphic
20171220 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
No Risk Areas Forecast
Probabilistic Damaging Wind Graphic
20171220 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 % 57,845 9,573,572 Atlanta, GA...Birmingham, AL...Sandy Springs, GA...Tuscaloosa, AL...Roswell, GA...
Probabilistic Large Hail Graphic
20171220 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
No Risk Areas Forecast
   SPC AC 200532

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1132 PM CST Tue Dec 19 2017

   Valid 201200Z - 211200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN
   MISSISSIPPI INTO NORTHERN GEORGIA...

   ...SUMMARY...
   A few strong to severe wind gusts are possible during the day on
   Wednesday from eastern Mississippi into northern Georgia.

   ...Synopsis and Discussion...
   A progressive yet weakening shortwave trough will move from the
   Lower MS Valley to the southern Appalachians by 00Z, with strong
   winds in the low levels that will veer with time, reducing shear. At
   the surface, a stationary front will extend across far northern MS,
   AL, and GA, and into SC for much of the day as a weak low translates
   eastward along it. South of this boundary will be a weakly unstable
   air mass characterized by mid 60s F dewpoints and poor low and
   midlevel lapse rates. 

   Storms now over eastern TX along the cold front are expected to be
   over MS by 12Z Wednesday, posing a marginal wind threat. Various
   CAMS solutions indicate that this activity should largely weaken
   with time, but a corridor of better lift along the east-west
   boundary across northern AL and GA may support a few strong wind
   gusts with storms on the warm side of the front. Otherwise, rapidly
   veering winds in the lower levels should effectively end any severe
   weather threat as the front/wind shift passes.

   ..Jewell/Leitman.. 12/20/2017

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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z