Alert archive / Louisiana / Mesoscale Discussions in 2021
Mesoscale Discussion 682
The Storm Prediction Center issued this mesoscale discussion at May 18, 2021, 10:39 PM CDT for 13 parishes in Louisiana; 6 counties in Texas. It was in force for 96 min.
The area
The outline as issued.
The facts
- Issued
- May 18, 2021, 10:39 PM CDT (03:39 UTC)
- Expired
- May 19, 2021, 12:15 AM CDT
- In force
- 96 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
Counties Acadia Parish, LA, Allen Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, Evangeline Parish, LA, Iberia Parish, LA, Jefferson Davis Parish, LA, Lafayette Parish, LA, Saint Landry Parish, LA, Saint Martin Parish, LA, Vermilion Parish, LA, Vernon Parish, LA, Hardin County, TX, Jasper County, TX, Jefferson County, TX, Newton County, TX, Orange County, TX, Tyler County, TX
The radar
The Lake Charles radar (KLCH), 19 km from the middle of the area, began a volume at 03:41 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
Lake Charles Mun, LA (KLCH), launched 00:00Z, 3.7 hours before the alert went out and 18 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
- 37 J/kg
- Mixed-layer CIN
- -296 J/kg
- Mixed-layer LCL
- 1094 m above ground
- 0-6 km bulk shear
- 33 kt
- 0-1 km storm-relative helicity
- -36 m²/s²
- 0-3 km storm-relative helicity
- 60 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- -0.0
The text
As transmitted.
769
ACUS11 KWNS 190340
SWOMCD
SPC MCD 190339
LAZ000-TXZ000-190515-
Mesoscale Discussion 0682
NWS Storm Prediction Center Norman OK
1039 PM CDT Tue May 18 2021
Areas affected...Far southeast TX into southwest LA
Concerning...Severe potential...Watch unlikely
Valid 190339Z - 190515Z
Probability of Watch Issuance...20 percent
SUMMARY...While an upstream MCS over southeast TX is expected to
gradually weaken as it approaches southwest LA, the threat for
isolated damaging wind gusts may persist into the early morning
hours. Watch issuance is not currently anticipated.
DISCUSSION...At 0330Z, an MCS is moving across southeast TX. As the
MCS moves eastward into southwest LA, it will encounter a less
unstable and more strongly capped (for surface-based parcels)
environment, with the more moist/unstable airmass expected to remain
near the immediate coast and offshore, to the south of a nearly
stationary surface boundary. As a result, a gradual weakening trend
is expected with time. While isolated damaging wind gusts may remain
possible into the early morning hours, the threat is expected to
become increasingly marginal, so additional watch issuance is
unlikely.
..Dean/Grams.. 05/19/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LIX...LCH...
LAT...LON 30939455 31169339 31199239 30719171 30029138 29419158
29419236 29379335 29369397 29909431 30939455SPC 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, 8:00 PM CDT | Mesoscale Discussion | SPC | Cherokee, Gregg, Harrison, Marion, Nacogdoches, Panola and 4 more | 60 min |
| May 18, 8:54 PM CDT | Mesoscale Discussion | SPC | Austin, Fort Bend, Harris, Jackson, Montgomery, Waller and 1 more | 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 Louisiana, 2021Mesoscale 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.