Alert archive / Texas / Mesoscale Discussions in 2021

Mesoscale Discussion 790

May 28, 202135 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at May 28, 2021, 5:54 PM CDT for 35 counties in Texas. It was in force for 96 min.

The area

The outline as issued.

The facts

Issued: May 28, 2021, 5:54 PM CDT (22:54 UTC)
Expired: May 28, 2021, 7:30 PM CDT
In force: 96 min
Issued by: the Storm Prediction Center
Concerning: Severe thunderstorm watch 218

All 35 counties

Atascosa County, TX, Austin County, TX, Bandera County, TX, Bastrop County, TX, Bexar County, TX, Blanco County, TX, Caldwell County, TX, Calhoun County, TX, Colorado County, TX, Comal County, TX, DeWitt County, TX, Edwards County, TX, Fayette County, TX, Fort Bend County, TX, Gillespie County, TX, Goliad County, TX, Gonzales County, TX, Guadalupe County, TX, Hays County, TX, Jackson County, TX, Karnes County, TX, Kendall County, TX, Kerr County, TX, Kimble County, TX, Lavaca County, TX, Lee County, TX, Llano County, TX, Mason County, TX, Matagorda County, TX, Medina County, TX, Real County, TX, Travis County, TX, Victoria County, TX, Wharton County, TX, Wilson County, TX

The radar

The Austin/San Antonio radar (KEWX), 51 km from the middle of the area, began a volume at 22:57 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.

The watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 221May 28, 6:20 PM CDT

The nearest sounding before it

Del Rio, TX (KDRT), launched 12:00Z, 10.9 hours before the alert went out and 233 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 3148 J/kg
Mixed-layer CIN: -194 J/kg
Mixed-layer LCL: 844 m above ground
0-6 km bulk shear: 42 kt
0-1 km storm-relative helicity: 125 m²/s²
0-3 km storm-relative helicity: 224 m²/s²
Significant tornado parameter: 0.1
Supercell composite: 3.1

Open this sounding in Storm Lab

The text

As transmitted.

320 
ACUS11 KWNS 282255
SWOMCD
SPC MCD 282254 
TXZ000-290030-

Mesoscale Discussion 0790
NWS Storm Prediction Center Norman OK
0554 PM CDT Fri May 28 2021

Areas affected...Parts of south central Texas into middle Texas
coastal areas

Concerning...Severe Thunderstorm Watch 218...

Valid 282254Z - 290030Z

The severe weather threat for Severe Thunderstorm Watch 218
continues.

SUMMARY...A new severe thunderstorm watch likely will be needed by 7
PM CDT, south of the current watch.  Strong thunderstorm development
posing a risk for large hail and locally damaging gusts will remain
possible into early evening, with potential for the evolution of a
larger, organizing cluster of storms while spreading southward this
evening, accompanied by increasing risk for strong surface gusts.

DISCUSSION...Individual storm motions have been relatively slow in
the presence of modest to weak (around 20 kt) westerly deep-layer
mean flow.  However, due to pronounced veering of winds with height
in lower to mid-levels, deep-layer shear remains strong and
supportive of evolving supercell structures.  Apparent moderate
southeasterly low-level inflow into the stronger storms emanates
from a seasonably moist boundary layer (lower to mid 70s dew
points).  Beneath steep mid-level lapse rates this is contributing
to large mixed-layer CAPE on the order of 2000-4000 J/kg.  

Thermodynamic profiles are similar southward into the Rio Grande
Valley and lower Texas coast, but with stronger capping beneath
gradually warmer elevated mixed-layer air.  However, a gradual
southward/southwestward suppression of this elevated mixed-layer air
is ongoing, which is expected to allow for a continued southward
progression of convective development, in addition to an eastward
and southeastward advection and propagation of cells into the 00-03Z
time frame.  

A gradual consolidation of convective outflow/surface cold pools
appears possible, which may contribute to further upscale convective
growth and accelerating forward propagation, accompanied by
increasing risk for damaging winds.  Otherwise, large hail and
localized potentially damaging wind gusts remains the primary threat
into early evening.

..Kerr.. 05/28/2021

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

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

LAT...LON   30770018 30899898 30509696 29559514 28299645 28479800
            29480001 30390064 30770018

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 27, 10:24 PM CDT	Mesoscale Discussion	SPC	Archer, Baylor, Clay, Haskell, Jack, Knox and 7 more	96 min
May 28, 2:33 AM CDT	Mesoscale Discussion	SPC	Collin, Denton, Hunt, Rockwall, Wise	117 min
May 28, 5:10 AM CDT	Mesoscale Discussion	SPC	Briscoe, Castro, Childress, Cottle, Floyd, Foard and 7 more	2 hr
May 28, 11:16 AM CDT	Mesoscale Discussion	SPC	Bell, Bosque, Brazos, Brown, Burleson, Coleman and 19 more	89 min
May 28, 12:14 PM CDT	Severe Thunderstorm Watch	SPC	Bell, Bosque, Brazos, Burleson, Burnet, Comanche and 22 more	7 hr
May 28, 12:49 PM CDT	Mesoscale Discussion	SPC	Brewster, Pecos, Presidio, Terrell	86 min
May 28, 1:03 PM CDT	Mesoscale Discussion	SPC	Andrews, Bailey, Borden, Cochran, Dawson, Ector and 11 more	57 min
May 28, 2:33 PM CDT	Mesoscale Discussion	SPC	Andrews, Borden, Brown, Coke, Coleman, Concho and 35 more	117 min
May 28, 2:45 PM CDT	Severe Thunderstorm Watch	SPC	Brewster, Culberson, Jeff Davis, Loving, Pecos, Reeves and 3 more	9 hr
May 28, 3:41 PM CDT	Severe Thunderstorm Watch	SPC	Andrews, Brown, Coke, Coleman, Concho, Crane and 20 more	8 hr
May 28, 3:42 PM CDT	Mesoscale Discussion	SPC	Bell, Brazos, Brown, Burleson, Burnet, Comanche and 12 more	93 min
May 28, 6:20 PM CDT	Severe Thunderstorm Watch	SPC	Atascosa, Austin, Bandera, Bastrop, Bexar, Blanco and 32 more	5 hr
May 28, 6:49 PM CDT	Mesoscale Discussion	SPC	Bailey, Deaf Smith, Parmer	86 min

Nearby

Mesoscale Discussions in Texas, 2021 Every mesoscale discussion in 2021

Sources

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.