Mesoscale Discussion 1910

Issued

Oct 27, 2021, 5:13 AM CDT (10:13 UTC)

Expired

Oct 27, 2021, 7:15 AM CDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe thunderstorm watch 539

The Austin/San Antonio radar (KEWX), 78 km from the middle of the area, began a volume at 10:12 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.

• Tornado Watch 540Oct 27, 7:55 AM CDT

573 
ACUS11 KWNS 271013
SWOMCD
SPC MCD 271013 
TXZ000-271215-

Mesoscale Discussion 1910
NWS Storm Prediction Center Norman OK
0513 AM CDT Wed Oct 27 2021

Areas affected...Parts of south central into southeastern Texas

Concerning...Severe Thunderstorm Watch 539...

Valid 271013Z - 271215Z

The severe weather threat for Severe Thunderstorm Watch 539
continues.

SUMMARY...An area of stronger thunderstorm activity could still
gradually intensify and organize across and east-northeast of the
San Antonio area into the mid/upper Texas coastal plain through
daybreak, accompanied by increasing risk for damaging wind gusts. 
While it is not yet certain that a new severe weather watch will be
needed, trends will continue to be monitored for this possibility.

DISCUSSION...Large-scale ascent and low-level low moistening appear
to be contributing to weakening mid-level inhibition ahead of
convective outflow advancing eastward and southeastward into the
Interstate-35 corridor of south central Texas.  Seasonably moist
surface dew points in the lower/mid 70s may be contributing to
mixed-layer CAPE in excess of 1500 J/kg, and perhaps as high as 3000
J/kg around the San Antonio area.  

While thunderstorm intensities along much of the convective outflow
boundary have remained fairly modest, a persistent area of stronger
convective development the past couple of hours has been focused
near the intersection of the outflow boundary and the leading edge
of cooling around the 700 mb level.  This mid-level cooling has
recently surged east of the Del Rio vicinity, with the clustering of
stronger storms now near/northwest through north of San Antonio.  

With this cooling forecast to continue to spread east-northeastward
toward the middle and upper Texas coastal plain through 12-14Z,
there appears potential for convection to begin to intensify more
rapidly with substantive further upscale growth.  If this occurs,
deep-layer shear beneath 30-50 kt southwesterly flow in the 500-300
mb layer appears sufficient to contribute to increasing organization
and the potential to produce strong surface gusts.

..Kerr.. 10/27/2021

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

ATTN...WFO...HGX...FWD...CRP...EWX...

LAT...LON   29379878 29809847 30059782 30629745 31139709 31319630
            31089546 30409531 29279614 28759705 28689880 29379878

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.