Alert archive / Louisiana / Mesoscale Discussions in 2021
Mesoscale Discussion 1913
The Storm Prediction Center issued this mesoscale discussion at Oct 27, 2021, 9:44 AM CDT for 4 counties in Arkansas; 13 parishes in Louisiana; 6 counties in Texas. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Oct 27, 2021, 9:44 AM CDT (14:44 UTC)
- Expired
- Oct 27, 2021, 11:45 AM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
All 23 counties
Columbia County, AR, Lafayette County, AR, Miller County, AR, Union County, AR, Bienville Parish, LA, Bossier Parish, LA, Caddo Parish, LA, Caldwell Parish, LA, Claiborne Parish, LA, De Soto Parish, LA, Jackson Parish, LA, Lincoln Parish, LA, Ouachita Parish, LA, Red River Parish, LA, Union Parish, LA, Webster Parish, LA, Winn Parish, LA, Bowie County, TX, Cass County, TX, Harrison County, TX, Marion County, TX, Panola County, TX, Shelby County, TX
The radar
The Shreveport radar (KSHV), 46 km from the middle of the area, began a volume at 14:46 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
Shreveport, LA (KSHV), launched 12:00Z, 2.7 hours before the alert went out and 37 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
- 395 J/kg
- Mixed-layer CIN
- -87 J/kg
- Mixed-layer LCL
- 557 m above ground
- 0-6 km bulk shear
- 38 kt
- 0-1 km storm-relative helicity
- 233 m²/s²
- 0-3 km storm-relative helicity
- 175 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 1.0
The text
As transmitted.
663
ACUS11 KWNS 271444
SWOMCD
SPC MCD 271444
LAZ000-ARZ000-TXZ000-271645-
Mesoscale Discussion 1913
NWS Storm Prediction Center Norman OK
0944 AM CDT Wed Oct 27 2021
Areas affected...far northeast TX into northern LA and southern AR
Concerning...Severe potential...Watch possible
Valid 271444Z - 271645Z
Probability of Watch Issuance...40 percent
SUMMARY...Sporadic strong wind gusts and/or a brief tornado will be
possible through the afternoon across far northeast Texas into
northern Louisiana and southern Arkansas.
DISCUSSION...Convection is slowly increasing in coverage and
intensity along a developing QLCS ahead of a surface cold front
across eastern TX. A narrow warm sector ahead of this activity will
propagate eastward through the day. Instability is forecast to
remain weak, generally around 1000 J/kg MLCAPE or less. However,
effective shear magnitudes around 40+ kt will be maintained, with
low level hodographs favorably curved for rotating cells within the
line of convection. Weaker instability and an overall less favorable
warm sector compared to further south will generally limit overall
severe potential, but a couple of locally damaging gusts or a brief
tornado will be possible with any stronger/better organized
convection that may develop. Convective trends are being monitored
and a watch may be needed within the next couple of hours.
..Leitman/Thompson.. 10/27/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...JAN...LZK...SHV...
LAT...LON 32799476 33219471 33439461 33619417 33709348 33559275
33309230 33069210 32699193 32369191 32129198 31919222
31859252 31859299 31719393 31749438 32019455 32489472
32799476SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Oct 27, 12:52 PM CDT | Mesoscale Discussion | SPC | Columbia, Lafayette, Miller, Union | 83 min |
| Oct 27, 7:36 AM CDT | Mesoscale Discussion | SPC | Acadia, Beauregard, Calcasieu, Cameron, Iberia, Jefferson Davis and 4 more | 84 min |
| Oct 27, 7:55 AM CDT | Tornado Watch | SPC | Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 13 more | 9 hr |
| Oct 27, 10:08 AM CDT | Tornado Watch | SPC | Bienville, Bossier, Caddo, Caldwell, Claiborne, De Soto and 6 more | 5 hr |
| Oct 27, 10:59 AM CDT | Mesoscale Discussion | SPC | Beauregard, Vernon | 91 min |
| Oct 27, 12:50 PM CDT | Mesoscale Discussion | SPC | Acadia, Ascension, Assumption, Avoyelles, Concordia, East Baton Rouge and 24 more | 85 min |
| Oct 27, 1:53 PM CDT | Tornado Watch | SPC | Ascension, Assumption, Catahoula, Concordia, East Baton Rouge, East Feliciana and 18 more | 8 hr |
| Oct 27, 3:25 PM CDT | Mesoscale Discussion | SPC | Ascension, Assumption, East Baton Rouge, East Feliciana, Iberville, Jefferson and 13 more | 95 min |
| Oct 27, 5:13 PM CDT | Mesoscale Discussion | SPC | Orleans, Saint Bernard, Saint John the Baptist, Saint Tammany, Tangipahoa, Washington | 2 hr |
| Oct 26, 7:23 PM CDT | Severe Thunderstorm Watch | SPC | Archer, Baylor, Brown, Callahan, Clay, Coke and 45 more | 8 hr |
| Oct 26, 9:37 PM CDT | Mesoscale Discussion | SPC | Archer, Baylor, Callahan, Clay, Coke, Coleman and 26 more | 83 min |
| Oct 27, 1:32 AM CDT | Severe Thunderstorm Watch | SPC | Anderson, Bastrop, Bell, Bexar, Blanco, Bosque and 48 more | 6 hr |
| Oct 27, 1:59 AM CDT | Mesoscale Discussion | SPC | Collin, Cooke, Dallas, Denton, Ellis, Grayson and 8 more | 91 min |
| Oct 27, 5:13 AM CDT | Mesoscale Discussion | SPC | Atascosa, Austin, Bastrop, Bexar, Brazos, Burleson and 22 more | 2 hr |
| Oct 27, 9:08 AM CDT | Mesoscale Discussion | SPC | Hardin, Jasper, Jefferson, Newton, Orange, Tyler | 97 min |
Nearby
Mesoscale Discussions in Louisiana, 2021Mesoscale Discussions in Texas, 2021Mesoscale Discussions in Arkansas, 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.