Alert archive / Texas / Mesoscale Discussions in 2021
Mesoscale Discussion 676
The Storm Prediction Center issued this mesoscale discussion at May 18, 2021, 5:10 PM CDT for La Salle County, McMullen County, Webb County, Texas. It was in force for 95 min.
The area
The outline as issued.
The facts
- Issued
- May 18, 2021, 5:10 PM CDT (22:10 UTC)
- Expired
- May 18, 2021, 6:45 PM CDT
- In force
- 95 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
Counties La Salle County, TX, McMullen County, TX, Webb County, TX
The radar
The Laughlin AFB radar (KDFX), 168 km from the middle of the area, began a volume at 22:14 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.
The nearest sounding before it
Corpus Christi, TX (KCRP), launched 12:00Z, 10.2 hours before the alert went out and 195 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.
- Mixed-layer CAPE
- 12 J/kg
- Mixed-layer CIN
- -595 J/kg
- Mixed-layer LCL
- 1962 m above ground
- 0-6 km bulk shear
- 46 kt
- 0-1 km storm-relative helicity
- -66 m²/s²
- 0-3 km storm-relative helicity
- -43 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.7
The text
As transmitted.
391
ACUS11 KWNS 182211
SWOMCD
SPC MCD 182210
TXZ000-182345-
Mesoscale Discussion 0676
NWS Storm Prediction Center Norman OK
0510 PM CDT Tue May 18 2021
Areas affected...South TX
Concerning...Severe potential...Watch possible
Valid 182210Z - 182345Z
Probability of Watch Issuance...40 percent
SUMMARY...A couple of supercells will be possible into early
evening, with a conditional risk of all hazards. Watch issuance is
possible soon.
DISCUSSION...At 22Z, convection is trying to deepen along a surface
boundary across Dimmit and Frio Counties, while a mature supercell
is noted across the international border south of Del Rio. MLCAPE of
2000-3000 J/kg and effective shear of 30-40 kt will favor a
supercell risk with any convection that can become sustained along
the boundary, though very dry midlevel air noted on WV imagery and a
tendency for the boundary to undercut developing cells as it sags
southward make it uncertain as to whether convection can mature.
If mature supercells can be sustained along the boundary, then the
environment would pose a conditional threat of all hazards. Watch
issuance is possible to cover this threat.
..Dean/Grams.. 05/18/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...CRP...EWX...
LAT...LON 28340030 28459956 28799880 28589838 28289832 27859857
27639886 27549916 27489950 27539983 27609999 28340030SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 17, 7:04 PM CDT | Mesoscale Discussion | SPC | Archer, Bosque, Brown, Clay, Comanche, Eastland and 15 more | 86 min |
| May 17, 7:23 PM CDT | Mesoscale Discussion | SPC | Carson, Dallam, Gray, Hansford, Hartley, Hemphill and 8 more | 2 hr |
| May 17, 7:32 PM CDT | Tornado Watch | SPC | Brown, Callahan, Coke, Coleman, Concho, McCulloch and 4 more | 3 hr |
| May 17, 7:37 PM CDT | Mesoscale Discussion | SPC | Callahan, Coke, Coleman, Glasscock, Howard, Jones and 6 more | 83 min |
| May 17, 8:04 PM CDT | Severe Thunderstorm Watch | SPC | Archer, Clay, Comanche, Eastland, Erath, Hamilton and 11 more | 5 hr |
| May 17, 8:34 PM CDT | Mesoscale Discussion | SPC | Atascosa, Dimmit, Frio, La Salle, McMullen, Maverick and 2 more | 116 min |
| May 17, 9:28 PM CDT | Mesoscale Discussion | SPC | Carson, Collingsworth, Donley, Gray, Hansford, Hemphill and 7 more | 2 hr |
| May 17, 9:44 PM CDT | Mesoscale Discussion | SPC | Armstrong, Borden, Briscoe, Childress, Collingsworth, Cottle and 15 more | 91 min |
| May 17, 10:23 PM CDT | Mesoscale Discussion | SPC | Archer, Brown, Callahan, Clay, Coke, Coleman and 16 more | 97 min |
| May 17, 10:35 PM CDT | Mesoscale Discussion | SPC | Andrews, Borden, Brewster, Crane, Crockett, Dawson and 13 more | 85 min |
| May 17, 10:58 PM CDT | Severe Thunderstorm Watch | SPC | Andrews, Borden, Brown, Coke, Coleman, Concho and 22 more | 7 hr |
| May 17, 11:37 PM CDT | Mesoscale Discussion | SPC | Bosque, Brown, Comanche, Denton, Eastland, Erath and 9 more | 83 min |
| May 18, 1:02 AM CDT | Mesoscale Discussion | SPC | Brooks, Duval, Jim Hogg | 58 min |
| May 18, 1:29 AM CDT | Mesoscale Discussion | SPC | Coke, Concho, Crane, Crockett, Ector, Glasscock and 13 more | 91 min |
| May 18, 5:07 AM CDT | Mesoscale Discussion | SPC | Coke, Concho, Irion, Reagan, Runnels, Schleicher and 2 more | 53 min |
| May 18, 1:18 PM CDT | Mesoscale Discussion | SPC | Atascosa, Austin, Bastrop, Bexar, Brazos, Burleson and 28 more | 117 min |
| May 18, 1:57 PM CDT | Mesoscale Discussion | SPC | Bailey, Castro, Deaf Smith, Parmer, Randall, Swisher | 3 hr |
| May 18, 2:29 PM CDT | Tornado Watch | SPC | Anderson, Atascosa, Austin, Bastrop, Bexar, Blanco and 30 more | 7 hr |
| May 18, 2:30 PM CDT | Mesoscale Discussion | SPC | Bowie, Camp, Cass, Cherokee, Franklin, Gregg and 12 more | 2 hr |
| May 18, 3:51 PM CDT | Severe Thunderstorm Watch | SPC | Bowie, Camp, Cass, Cherokee, Franklin, Gregg and 11 more | 5 hr |
| May 18, 3:52 PM CDT | Mesoscale Discussion | SPC | Bastrop, Caldwell, Colorado, Fayette, Gonzales, Guadalupe and 2 more | 83 min |
| May 18, 5:39 PM CDT | Mesoscale Discussion | SPC | Bowie, Cass, Gregg, Harrison, Marion, Morris and 1 more | 2 hr |
| May 18, 6:07 PM CDT | Mesoscale Discussion | SPC | Armstrong, Borden, Briscoe, Carson, Castro, Cochran and 17 more | 113 min |
| May 18, 6:13 PM CDT | Mesoscale Discussion | SPC | Austin, Brazos, Burleson, Colorado, DeWitt, Fayette and 14 more | 92 min |
Nearby
Mesoscale Discussions in Texas, 2021Every 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.