Alert archive / Texas / Mesoscale Discussions in 2021
Mesoscale Discussion 680
The Storm Prediction Center issued this mesoscale discussion at May 18, 2021, 8:00 PM CDT for 10 counties in Texas. It was in force for 60 min.
The area
The outline as issued.
The facts
- Issued
- May 18, 2021, 8:00 PM CDT (01:00 UTC)
- Expired
- May 18, 2021, 9:00 PM CDT
- In force
- 60 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 189
Counties Cherokee County, TX, Gregg County, TX, Harrison County, TX, Marion County, TX, Nacogdoches County, TX, Panola County, TX, Rusk County, TX, Shelby County, TX, Smith County, TX, Upshur County, TX
The radar
The Shreveport radar (KSHV), 87 km from the middle of the area, began a volume at 00:59 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 nearest sounding before it
Shreveport, LA (KSHV), launched 00:00Z, 1.0 hours before the alert went out and 96 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
- 608 J/kg
- Mixed-layer CIN
- -27 J/kg
- Mixed-layer LCL
- 863 m above ground
- 0-6 km bulk shear
- 9 kt
- 0-1 km storm-relative helicity
- 56 m²/s²
- 0-3 km storm-relative helicity
- 102 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
627
ACUS11 KWNS 190101
SWOMCD
SPC MCD 190100
LAZ000-TXZ000-190200-
Mesoscale Discussion 0680
NWS Storm Prediction Center Norman OK
0800 PM CDT Tue May 18 2021
Areas affected...The Arklatex region
Concerning...Severe Thunderstorm Watch 189...
Valid 190100Z - 190200Z
The severe weather threat for Severe Thunderstorm Watch 189
continues.
SUMMARY...The severe threat continues to decline for most of WW 189,
but an isolated wind/hail threat remains possible for parts of the
Arklatex region through the late evening hours.
DISCUSSION...Lightning and IR trends continue to show a gradual
weakening of the QLCS across central AR, and sub-severe winds
recently reported with the line further support this idea. Diurnal
cooling will continue to diminish MLCAPE through the late evening
hours across much of AR, which will further act to mitigate the
severe potential across much of WW 189. Further south across the
Arklatex region, around 1000 J/kg MLCAPE along with 25-35 knots of
effective bulk shear are noted in RAP mesoanalysis ahead of a
cluster of storms emerging out of central TX. While this cluster has
largely exhibited only loose organization, it is forecast to
propagate into parts of the Arklatex area over the next 1-2 hours.
Although confidence is low, isolated instances of severe wind/hail
will remain possible given the environment.
..Moore.. 05/19/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...SHV...HGX...FWD...
LAT...LON 32259559 32669540 32969487 32999432 32689393 32289391
31909383 31409424 31329493 31679539 32259559SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 18, 7:34 PM CDT | Tornado Watch | SPC | Austin, Bee, Brazoria, Chambers, Colorado, Fort Bend and 17 more | 6 hr |
| May 18, 8:54 PM CDT | Mesoscale Discussion | SPC | Austin, Fort Bend, Harris, Jackson, Montgomery, Waller and 1 more | 96 min |
| May 18, 10:39 PM CDT | Mesoscale Discussion | SPC | Hardin, Jasper, Jefferson, Newton, Orange, Tyler | 96 min |
| May 18, 11:00 PM CDT | Mesoscale Discussion | SPC | Dimmit, Duval, Jim Hogg, La Salle, Webb, Zapata | 90 min |
| May 19, 3:32 AM CDT | Mesoscale Discussion | SPC | Brooks, Dimmit, Duval, Hidalgo, Jim Hogg, Jim Wells and 5 more | 118 min |
| May 19, 5:24 AM CDT | Severe Thunderstorm Watch | SPC | Brooks, Cameron, Duval, Hidalgo, Jim Hogg, Jim Wells and 8 more | 8 hr |
| May 19, 7:09 AM CDT | Mesoscale Discussion | SPC | Hidalgo, Jim Hogg, Starr | 96 min |
| May 19, 8:46 AM CDT | Mesoscale Discussion | SPC | Brooks, Cameron, Hidalgo, Kenedy, Willacy | 89 min |
| May 19, 2:10 PM CDT | Mesoscale Discussion | SPC | Callahan, Coke, Coleman, Concho, Crane, Crockett and 24 more | 3 hr |
| May 19, 6:06 PM CDT | Mesoscale Discussion | SPC | Crane, Crockett, Ector, Glasscock, Irion, Midland and 6 more | 84 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.