May 11, 2021 1630 UTC Day 1 Convective Outlook
Updated: Tue May 11 16:26:55 UTC 2021 (20210511 1630Z Day 1 shapefile | 20210511 1630Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20210511 1630 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 91,230 6,749,697 San Antonio, TX...Austin, TX...Laredo, TX...Waco, TX...Killeen, TX...
MARGINAL 234,127 27,353,994 Houston, TX...Dallas, TX...Jacksonville, FL...Fort Worth, TX...New Orleans, LA...
Probabilistic Tornado Graphic
20210511 1630 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 % 38,885 3,666,887 Baton Rouge, LA...Laredo, TX...Lafayette, LA...College Station, TX...The Woodlands, TX...
Probabilistic Damaging Wind Graphic
20210511 1630 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
15 % 25,942 2,424,618 San Antonio, TX...Laredo, TX...Schertz, TX...Seguin, TX...Alice, TX...
5 % 250,989 28,043,785 Houston, TX...Dallas, TX...Jacksonville, FL...Austin, TX...Fort Worth, TX...
Probabilistic Large Hail Graphic
20210511 1630 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
SIG SEVERE 6,020 31,201 Eagle Pass, TX...
15 % 91,278 6,750,701 San Antonio, TX...Austin, TX...Laredo, TX...Waco, TX...Killeen, TX...
5 % 234,336 27,363,692 Houston, TX...Dallas, TX...Jacksonville, FL...Fort Worth, TX...New Orleans, LA...
   SPC AC 111626

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1126 AM CDT Tue May 11 2021

   Valid 111630Z - 121200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THROUGH THIS
   EVENING FOR PARTS OF CENTRAL AND SOUTH TX...

   ...SUMMARY...
   Large hail will be possible today across central Texas, while large
   hail and damaging gusts may occur later this afternoon/evening
   across parts of south central Texas.  More isolated severe storms
   will be possible farther east into the lower Mississippi Valley and
   the Southeast.

   ...TX to the lower MS Valley through tonight...
   Multiple clusters of elevated thunderstorms are ongoing from the
   Edwards Plateau in TX northeastward into OK in association with
   850-700 mb warm advection, downstream from a series of subtle
   southern-stream speed maxima ejecting eastward in advance of a
   midlevel trough over UT/CO.  Other clusters of storms have shown
   signs of slow weakening across southern LA in a weak low-level warm
   advection zone north of a surface front that is sagging southward. 
   The slow-moving front extends westward across southeast TX and
   southwestward into south central TX.  South of the front, an influx
   of mid 70s boundary-layer dewpoints continues from the Gulf of
   Mexico, beneath an elevated mixed layer extending northeastward over
   TX from northern Mexico.

   The combination of steep midlevel lapse rates and moisture influx
   into the warm advection zone atop the frontal surface will continue
   to support elevated thunderstorms spreading eastward from TX to the
   lower MS Valley through tonight.  The more consistent threat for
   large hail with the stronger elevated storms will be today across TX
   where moderate buoyancy remains aloft, prior to more widespread
   convective overturning and reduction of midlevel lapse rates. 
   Farther south along the front, moderate-strong buoyancy (MLCAPE up
   to 3000 J/kg) is expected with daytime heating from portions of the
   Rio Grande Valley into southeast TX.  Isolated storms may form along
   the front and pose a large hail threat.  There is also a chance for
   mergers of the frontal storms with convection originating east of
   the higher terrain in northeast Mexico, which could lead to the
   development of a larger cluster this evening across south central
   TX.

   ...Southern AL/FL Panhandle to southern GA this afternoon...
   Isolated strong-severe storms will be possible within and east of a
   cluster of storms moving eastward over the MS coast as of late
   morning, as well as along and south of a diffuse boundary across
   southern GA.  Effective bulk shear of 25-35 kt and MLCAPE of
   1000-1500 J/kg will support the potential for isolated large
   hail/damaging gusts.

   ..Thompson/Moore.. 05/11/2021

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z