Alert archive / Louisiana / Mesoscale Discussions in 2021

Mesoscale Discussion 1916

October 27, 20214 counties in Arkansas; 13 parishes in Louisiana; 6 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Oct 27, 2021, 12:52 PM CDT for 4 counties in Arkansas; 13 parishes in Louisiana; 6 counties in Texas. It was in force for 83 min.

The area

The outline as issued.

The facts

Issued: Oct 27, 2021, 12:52 PM CDT (17:52 UTC)
Expired: Oct 27, 2021, 2:15 PM CDT
In force: 83 min
Issued by: the Storm Prediction Center
Concerning: Tornado watch 541

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 17:55 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 12:00Z, 5.9 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

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

Open this sounding in Storm Lab

The text

As transmitted.

727 
ACUS11 KWNS 271753
SWOMCD
SPC MCD 271752 
LAZ000-ARZ000-TXZ000-271915-

Mesoscale Discussion 1916
NWS Storm Prediction Center Norman OK
1252 PM CDT Wed Oct 27 2021

Areas affected...portions of northern LA

Concerning...Tornado Watch 541...

Valid 271752Z - 271915Z

The severe weather threat for Tornado Watch 541 continues.

SUMMARY...A couple of locally strong wind gusts are possible the
next hour or two across Tornado Watch 541, but the overall severe
threat will diminish with eastward extent across northeast
Louisiana.

DISCUSSION...Instability continues to wane downstream from Tornado
Watch 541 as the warm sector becomes increasingly narrow. A warm
front draped across south/southeastern LA will slowly lift northward
during the afternoon, but not quickly enough as the ongoing line of
convection advances eastward faster than the front advances
northward. As a result, the boundary layer is expected to remain
rather cool and only weakly unstable. Weak to moderate vertical
shear will remain over the region and a couple of strong storms may
persist within the line in the short-term, possibly producing
locally gusty winds. However, the overall severe threat is expected
to be limited across northeast LA and a downstream watch is not
expected.

..Leitman.. 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
            32799476

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Oct 27, 9:44 AM CDT	Mesoscale Discussion	SPC	Columbia, Lafayette, Miller, Union	2 hr
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, 2021 Mesoscale Discussions in Texas, 2021 Mesoscale Discussions in Arkansas, 2021 Every 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.