Mesoscale Discussion 592

Issued

May 11, 2021, 1:22 PM CDT (18:22 UTC)

Expired

May 11, 2021, 3:45 PM CDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch possible

Chance of a watch

40%

Counties Dimmit County, TX, Kinney County, TX, Maverick County, TX, Terrell County, TX, Val Verde County, TX, Zavala County, TX

The Laughlin AFB radar (KDFX), 101 km from the middle of the area, began a volume at 18:21 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

• Severe Thunderstorm Watch 165May 11, 3:40 PM CDT

443 
ACUS11 KWNS 111823
SWOMCD
SPC MCD 111822 
TXZ000-112045-

Mesoscale Discussion 0592
NWS Storm Prediction Center Norman OK
0122 PM CDT Tue May 11 2021

Areas affected...Parts of the lower Pecos into lower Rio Grande
Valley vicinity

Concerning...Severe potential...Watch possible 

Valid 111822Z - 112045Z

Probability of Watch Issuance...40 percent

SUMMARY...Intense thunderstorms are initiating, mainly across the
higher terrain of Coahuila, but may be slow to develop eastward. 
Once a propagation into lower elevations commences, activity
probably will pose a risk for large hail and strong wind gusts
across and east of the Rio Grande River.  It is possible that this
might not occur until after 4-5 PM CDt.

DISCUSSION...Thunderstorms are initiating along the higher terrain,
as far north as the lower Pecos Valley, but generally southeast
through south of the Texas Big Bend, across Coahuila.  Mid 70s
surface dew points have advected west of the Rio Grande, toward the
higher terrain, contributing to large CAPE in excess of 3000 J/kg,
in the presence of steep lower/mid tropospheric.

Given somewhat modest (20-30 kt) west-southwesterly ambient
deep-layer mean flow, and lingering inhibition associated with
elevated mixed-layer air to the east of the higher terrain, activity
might be slow to develop off the higher terrain.  However, given the
the number of storms, merging convection and consolidating outflows
probably will contribute to upscale growth that should eventually
surge off the higher terrain, into and across the Rio Grande Valley
later this afternoon.  It remains unclear just how this might
evolve, but there appears strong enough shear beneath the
subtropical jet, across and south of the Del Rio vicinity, to
support the evolution of an organized convective system, perhaps
preceded by discrete supercell development.  Some of this activity
may pose a risk for large hail in excess of 2 inches in diameter,
along with strong, damaging wind gusts.

..Kerr/Thompson.. 05/11/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...CRP...EWX...SJT...MAF...

LAT...LON   29500229 30240282 30520198 30100107 29550044 29059980
            28469944 27889936 27569977 26830047 27320138 27530166
            27790172 28740195 29500229

Mesoscale Discussions in Texas, 2021Every mesoscale discussion in 2021

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.