Alert archive / Texas / Mesoscale Discussions in 2021
Mesoscale Discussion 201
The Storm Prediction Center issued this mesoscale discussion at Mar 17, 2021, 11:35 AM CDT for 14 parishes in Louisiana; 16 counties in Texas. It was in force for 85 min.
The area
The outline as issued.
The facts
- Issued
- Mar 17, 2021, 11:35 AM CDT (16:35 UTC)
- Expired
- Mar 17, 2021, 1:00 PM CDT
- In force
- 85 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 28
All 30 counties
Allen Parish, LA, Beauregard Parish, LA, Bienville Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, De Soto Parish, LA, Grant Parish, LA, Jackson Parish, LA, Natchitoches Parish, LA, Rapides Parish, LA, Red River Parish, LA, Sabine Parish, LA, Vernon Parish, LA, Winn Parish, LA, Angelina County, TX, Brazoria County, TX, Chambers County, TX, Galveston County, TX, Hardin County, TX, Harris County, TX, Jasper County, TX, Jefferson County, TX, Liberty County, TX, Newton County, TX, Orange County, TX, Polk County, TX, Sabine County, TX, San Augustine County, TX, Shelby County, TX, Tyler County, TX
The radar
The Lake Charles radar (KLCH), 86 km from the middle of the area, began a volume at 16:38 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
Lake Charles Mun, LA (KLCH), launched 12:00Z, 4.6 hours before the alert went out and 87 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
- 458 J/kg
- Mixed-layer CIN
- -397 J/kg
- Mixed-layer LCL
- 1132 m above ground
- 0-6 km bulk shear
- 47 kt
- 0-1 km storm-relative helicity
- 158 m²/s²
- 0-3 km storm-relative helicity
- 247 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 2.2
The text
As transmitted.
722
ACUS11 KWNS 171636
SWOMCD
SPC MCD 171635
LAZ000-TXZ000-171800-
Mesoscale Discussion 0201
NWS Storm Prediction Center Norman OK
1135 AM CDT Wed Mar 17 2021
Areas affected...Southeast Texas and western Louisiana
Concerning...Tornado Watch 28...
Valid 171635Z - 171800Z
The severe weather threat for Tornado Watch 28 continues.
SUMMARY...A new watch may be needed south of Watch 28 across
southeast Texas and western Louisiana.
DISCUSSION...The well-developed squall line has started to break up
and weaken across northern Louisiana and southern Arkansas where the
line has moved ahead of the front. However, stronger storms continue
farther south where storms are closer to the surface front in an
area of greater low-level convergence. These storms extend into
southeast Texas where no watch is currently in effect and thus a new
watch may need to be issued soon. The current tornado threat is
somewhat lower with southern extent as low-level wind fields are
quite unidirecitonal. However, the low-level jet is expected to
strengthen over the next few hours which may increase the tornado
threat. Damaging winds and large hail will be the primary threat in
the near term given around 1000 to 1500 J/kg MLCAPE and effective
shear around 50 knots.
..Bentley/Grams.. 03/17/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LCH...SHV...HGX...
LAT...LON 32629374 32689292 32349220 31719225 30239289 29739311
29669383 29369449 28979509 28869532 29079582 29729573
32629374SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 17, 1:32 AM CDT | Mesoscale Discussion | SPC | Bienville, Bossier, Caddo, Claiborne, De Soto, Jackson and 6 more | 118 min |
| Mar 17, 4:04 AM CDT | Mesoscale Discussion | SPC | Bossier, Caddo | 86 min |
| Mar 17, 4:37 AM CDT | Severe Thunderstorm Watch | SPC | Bossier, Caddo | 5 hr |
| Mar 17, 6:40 AM CDT | Mesoscale Discussion | SPC | Bossier, Caddo, Claiborne, Webster | 95 min |
| Mar 17, 8:43 AM CDT | Tornado Watch | SPC | Bienville, Bossier, Caddo, Claiborne, De Soto, Jackson and 8 more | 4 hr |
| Mar 17, 11:53 AM CDT | Tornado Watch | SPC | Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 7 more | 6 hr |
| Mar 17, 12:15 PM CDT | Mesoscale Discussion | SPC | Caldwell, Catahoula, East Carroll, Franklin, Jackson, LaSalle and 9 more | 90 min |
| Mar 17, 12:57 PM CDT | Tornado Watch | SPC | Bienville, Caldwell, Catahoula, Concordia, East Carroll, Franklin and 15 more | 6 hr |
| Mar 17, 1:45 PM CDT | Mesoscale Discussion | SPC | Ascension, Assumption, East Baton Rouge, East Feliciana, Iberia, Iberville and 18 more | 90 min |
| Mar 17, 2:38 PM CDT | Tornado Watch | SPC | Ascension, Assumption, East Baton Rouge, East Feliciana, Iberia, Iberville and 19 more | 8 hr |
| Mar 17, 2:56 PM CDT | Mesoscale Discussion | SPC | Caldwell, Catahoula, Concordia, East Carroll, Franklin, Grant and 7 more | 94 min |
| Mar 16, 7:49 PM CDT | Severe Thunderstorm Watch | SPC | Collingsworth, Donley, Gray, Hemphill, Lipscomb, Roberts and 1 more | 7 hr |
| Mar 16, 9:27 PM CDT | Mesoscale Discussion | SPC | Archer, Baylor, Brown, Callahan, Coke, Coleman and 30 more | 93 min |
| Mar 16, 10:26 PM CDT | Severe Thunderstorm Watch | SPC | Bell, Bosque, Brown, Callahan, Coke, Coleman and 44 more | 7 hr |
| Mar 17, 2:20 AM CDT | Mesoscale Discussion | SPC | Brown, Callahan, Coleman, Comanche, Eastland, Erath and 6 more | 85 min |
| Mar 17, 4:38 AM CDT | Mesoscale Discussion | SPC | Armstrong, Carson, Dallam, Deaf Smith, Gray, Hansford and 11 more | 6 hr |
Nearby
Mesoscale Discussions in Texas, 2021Mesoscale Discussions in Louisiana, 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.