Day 1 Outlook Day 2 Outlook Day 3 Outlook Days 4-8 Outlook

Day 1 Outlook Convective Tornado
Hail Wind
Categorical Day1 2000Z Outlook
Images courtesy of the NWS Storm Prediction Center
 Forecast Discussion

ACUS01 KWNS 112154
SPC AC 112153

Day 1 Convective Outlook AMEND 1
NWS Storm Prediction Center Norman OK
0453 PM CDT Tue May 11 2021

Valid 112150Z - 121200Z



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.

...2150Z update...
Extended Slight Risk into western Louisiana ahead of an organized
line of severe storms. For more information see mesoscale discussion

...20Z update...
Minor adjustments were made to clear severe from parts of northwest
Texas in the wake of the ongoing storms now moving across north
Texas. Otherwise, substantial instability remains across the Slight
Risk area south of the cold front, with sufficient deep-layer shear
to support severe storms. Isolated supercells remain possible ahead
of the front into east Texas, and with activity developing over
Mexico which will threaten the Rio Grande Valley later today.

The Slight Risk was also expanded a bit across Deep South Texas, in
deference to the very strong instability which could fuel an MCS
later tonight as the front continues south, and possibly interacts
with activity/outflow moving out of Mexico. Capping is forecast to
remain weak, supporting southeastward propagation. Damaging winds
will be possible.

For more information on the Rio Grande Valley, southern Alabama, and
east Texas, see mesoscale discussions 592, 593, and 594

..Jewell.. 05/11/2021

.PREV DISCUSSION... /ISSUED 1126 AM CDT Tue May 11 2021/

...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

...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.