Alert archive / Louisiana / Mesoscale Discussions in 2021
Mesoscale Discussion 2017
The Storm Prediction Center issued this mesoscale discussion at Dec 11, 2021, 4:02 AM CST for 15 parishes in Louisiana; 11 counties in Texas. It was in force for 118 min.
The area
The outline as issued.
The facts
- Issued
- Dec 11, 2021, 4:02 AM CST (10:02 UTC)
- Expired
- Dec 11, 2021, 6:00 AM CST
- In force
- 118 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
All 26 counties
Allen Parish, LA, Avoyelles Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Caldwell Parish, LA, Catahoula Parish, LA, Concordia Parish, LA, Evangeline Parish, LA, Grant Parish, LA, LaSalle Parish, LA, Natchitoches Parish, LA, Rapides Parish, LA, Sabine Parish, LA, Vernon Parish, LA, Winn Parish, LA, Hardin County, TX, Jasper County, TX, Liberty County, TX, Montgomery County, TX, Newton County, TX, Orange County, TX, Polk County, TX, Sabine County, TX, San Augustine County, TX, San Jacinto County, TX, Tyler County, TX
The radar
The Ft Polk radar (KPOE), 31 km from the middle of the area, began a volume at 10:06 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, 10.0 hours before the alert went out and 101 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
- 2052 J/kg
- Mixed-layer CIN
- 0 J/kg
- Mixed-layer LCL
- 482 m above ground
- 0-6 km bulk shear
- 48 kt
- 0-1 km storm-relative helicity
- 196 m²/s²
- 0-3 km storm-relative helicity
- 209 m²/s²
- Significant tornado parameter
- 2.7
- Supercell composite
- 10.1
The text
As transmitted.
853
ACUS11 KWNS 111002
SWOMCD
SPC MCD 111002
LAZ000-MSZ000-TXZ000-111200-
Mesoscale Discussion 2017
NWS Storm Prediction Center Norman OK
0402 AM CST Sat Dec 11 2021
Areas affected...portions of far eastern Texas into northern and
central Louisiana
Concerning...Severe potential...Watch unlikely
Valid 111002Z - 111200Z
Probability of Watch Issuance...20 percent
SUMMARY...A couple damaging gusts or a brief tornado cannot be
completely ruled out with the strongest storms, though a more
widespread severe event and a WW issuance is not currently
anticipated.
DISCUSSION...An organized squall line continues to sag southeastward
across far east Texas into northwest Louisiana within a buoyancy
axis, characterized by 1500+ J/kg MLCAPE (per 09Z mesoanalysis).
Despite the modest buoyancy, deep-layer ascent remains weak.
Nonetheless, 50+ kts of effective bulk shear persists across the
region, and a damaging gust or perhaps a brief tornado cannot be
completely ruled out with one or two of the strongest embedded
storms. Convective trends will continue to be monitored, but an
organized severe threat and WW issuance is not currently expected in
association with this segment of the squall line.
..Squitieri/Edwards.. 12/11/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...JAN...LIX...LCH...SHV...HGX...
LAT...LON 30089585 31579398 32099305 32199234 32129168 31819137
31359135 30749193 30289291 30059405 29959484 30089585SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Dec 10, 10:00 PM CST | Mesoscale Discussion | SPC | Bienville, Bossier, Caddo, Caldwell, Claiborne, De Soto and 16 more | 90 min |
| Dec 10, 10:44 PM CST | Tornado Watch | SPC | Bienville, Bossier, Caddo, Claiborne, Jackson, Lincoln and 4 more | 6 hr |
| Dec 11, 1:36 AM CST | Mesoscale Discussion | SPC | Beauregard, Caldwell, De Soto, Grant, LaSalle, Natchitoches and 4 more | 114 min |
| Dec 11, 2:00 AM CST | Mesoscale Discussion | SPC | Bienville, Bossier, Claiborne, Lincoln, Morehouse, Ouachita and 3 more | 90 min |
| Dec 10, 6:34 PM CST | Tornado Watch | SPC | Bowie, Camp, Cass, Franklin, Marion, Morris and 4 more | 4 hr |
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.