Alert archive / Texas / Severe Thunderstorm Watches in 2021

Severe Thunderstorm Watch 83

April 9, 202117 parishes in Louisiana; 22 counties in Texas

The Storm Prediction Center issued this severe thunderstorm watch at Apr 9, 2021, 5:32 PM CDT for 17 parishes in Louisiana; 22 counties in Texas. It was in force for 7 hr.

The area

The outline as issued.

The facts

Issued
Apr 9, 2021, 5:32 PM CDT (22:32 UTC)
Expired
Apr 10, 2021, 1:00 AM CDT
In force
7 hr
Issued by
the Storm Prediction Center
Largest hail expected
2 in
Strongest gust expected
65 kt
All 39 counties

Bienville Parish, LA, Bossier Parish, LA, Caddo Parish, LA, Caldwell Parish, LA, Claiborne Parish, LA, De Soto Parish, LA, Grant Parish, LA, Jackson Parish, LA, LaSalle Parish, LA, Lincoln Parish, LA, Natchitoches Parish, LA, Ouachita Parish, LA, Red River Parish, LA, Sabine Parish, LA, Union Parish, LA, Webster Parish, LA, Winn Parish, LA, Angelina County, TX, Brazos County, TX, Burleson County, TX, Cherokee County, TX, Gregg County, TX, Grimes County, TX, Harrison County, TX, Houston County, TX, Madison County, TX, Marion County, TX, Nacogdoches County, TX, Panola County, TX, Polk County, TX, Rusk County, TX, Sabine County, TX, San Augustine County, TX, San Jacinto County, TX, Shelby County, TX, Smith County, TX, Trinity County, TX, Walker County, TX, Washington County, TX

The radar

The Ft Polk radar (KPOE), 93 km from the middle of the area, began a volume at 22:33 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.

What SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes
20%
One or more EF2 to EF5 tornadoes
10%
Ten or more severe wind reports
40%
One or more gusts of 65 knots or more
40%
Ten or more severe hail reports
40%
One or more hailstones of 2 inches or more
40%
Six or more combined severe hail and wind reports
70%

Warnings issued inside it

29 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

IssuedProductOfficeCountiesLasted
Apr 9, 5:38 PM CDTSevere Thunderstorm WarningSHVBossier, Claiborne, Webster67 min
Apr 9, 5:44 PM CDTSevere Thunderstorm WarningSHVOuachita, Union46 min
Apr 9, 5:49 PM CDTSevere Thunderstorm WarningSHVDe Soto56 min
Apr 9, 5:54 PM CDTSevere Thunderstorm WarningSHVCaldwell, Jackson, Ouachita, Winn66 min
Apr 9, 5:57 PM CDTSevere Thunderstorm WarningHGXHouston, Trinity33 min
Apr 9, 5:58 PM CDTSevere Thunderstorm WarningSHVUnion21 min
Apr 9, 6:01 PM CDTSevere Thunderstorm WarningSHVPanola, Rusk, Shelby59 min
Apr 9, 6:23 PM CDTSevere Thunderstorm WarningSHVBienville, Jackson, Lincoln, Natchitoches, Red River, Winn52 min
Apr 9, 6:33 PM CDTFlash Flood WarningSHVCherokee, Nacogdoches, Panola, Rusk, Smith3 hr
Apr 9, 6:40 PM CDTSevere Thunderstorm WarningSHVBienville, Claiborne, Lincoln, Union65 min
Apr 9, 6:49 PM CDTSevere Thunderstorm WarningSHVBienville, Caddo, De Soto, Red River56 min
Apr 9, 6:53 PM CDTSevere Thunderstorm WarningSHVPanola, Rusk45 min
Apr 9, 6:55 PM CDTSevere Thunderstorm WarningSHVOuachita, Union65 min
Apr 9, 7:11 PM CDTSevere Thunderstorm WarningSHVDe Soto, Natchitoches, Red River, Sabine64 min
Apr 9, 7:11 PM CDTSevere Thunderstorm WarningSHVGregg, Harrison, Rusk27 min
Apr 9, 7:18 PM CDTSevere Thunderstorm WarningSHVCaldwell, Jackson, Ouachita42 min
Apr 9, 7:35 PM CDTFlash Flood WarningSHVCaldwell, Jackson, Lincoln, Ouachita, Union, Winn3 hr
Apr 9, 7:40 PM CDTSevere Thunderstorm WarningSHVBienville, Natchitoches, Red River, Winn42 min
Apr 9, 7:55 PM CDTSevere Thunderstorm WarningSHVBienville, Grant, Jackson, Natchitoches, Winn65 min
Apr 9, 7:57 PM CDTSevere Thunderstorm WarningSHVCaldwell, Ouachita22 min
Apr 9, 8:08 PM CDTSevere Thunderstorm WarningSHVAngelina, Nacogdoches, San Augustine42 min
Apr 9, 8:43 PM CDTSevere Thunderstorm WarningSHVCaldwell, Ouachita, Winn62 min
Apr 9, 10:02 PM CDTSevere Thunderstorm WarningSHVCherokee, Nacogdoches, Rusk58 min
Apr 9, 10:27 PM CDTSevere Thunderstorm WarningSHVGrant, LaSalle40 min
Apr 9, 10:29 PM CDTSevere Thunderstorm WarningHGXHouston46 min
Apr 9, 10:50 PM CDTSevere Thunderstorm WarningSHVNacogdoches, Rusk, San Augustine, Shelby55 min
Apr 9, 11:42 PM CDTSevere Thunderstorm WarningSHVCaddo63 min
Apr 9, 11:47 PM CDTSevere Thunderstorm WarningSHVCamp, Franklin, Gregg, Smith, Upshur, Wood43 min
Apr 10, 12:45 AM CDTSevere Thunderstorm WarningSHVLaSalle45 min

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Shreveport, LA (KSHV), launched 12:00Z, 10.5 hours before the alert went out and 110 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-pSkew-T log-p diagram, Shreveport, LA at 12:00Z on 2021-04-09Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 928 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Shreveport, LA at 12:00Z on 2021-04-09The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 6 square meters per square second.1939587897Sfc1 km3 km6 km9 kmRMLM
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
928 J/kg
Mixed-layer CIN
-310 J/kg
Mixed-layer LCL
1043 m above ground
0-6 km bulk shear
37 kt
0-1 km storm-relative helicity
6 m²/s²
0-3 km storm-relative helicity
61 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

735 
WWUS20 KWNS 092229
SEL3  
SPC WW 092229
LAZ000-TXZ000-100400-

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 83
NWS Storm Prediction Center Norman OK
530 PM CDT Fri Apr 9 2021

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  Northern Louisiana
  East Texas

* Effective this Friday afternoon and evening from 530 PM until
  1100 PM CDT.

* Primary threats include...
  Scattered damaging winds and isolated significant gusts to 75
    mph possible
  Scattered large hail and isolated very large hail events to 2
    inches in diameter possible
  A tornado or two possible

SUMMARY...Multiple clusters along modifying outflow will pose a risk
for mainly large hail and locally damaging winds. Convection may
grow upscale into an MCS towards late evening with an increasing
severe threat.

The severe thunderstorm watch area is approximately along and 40
statute miles north and south of a line from 15 miles south of
Monroe LA to 15 miles west of College Station TX. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU3).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.

&&

OTHER WATCH INFORMATION...CONTINUE...WW 76...WW 77...WW 78...WW
79...WW 80...WW 81...WW 82...

AVIATION...A few severe thunderstorms with hail surface and aloft to
2 inches. Extreme turbulence and surface wind gusts to 65 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
27025.

...Grams

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 9, 2:49 AM CDTMesoscale DiscussionSPCJefferson, Plaquemines, Saint Bernard2 hr
Apr 9, 9:49 AM CDTMesoscale DiscussionSPCBossier, Caddo116 min
Apr 9, 12:07 PM CDTSevere Thunderstorm WatchSPCBienville, Bossier, Caddo, Claiborne, De Soto, Jackson and 5 more6 hr
Apr 9, 1:25 PM CDTMesoscale DiscussionSPCBienville, Bossier, Caldwell, Claiborne, De Soto, East Carroll and 12 more95 min
Apr 9, 3:10 PM CDTMesoscale DiscussionSPCClaiborne, East Carroll, Lincoln, Morehouse, Ouachita, Richland and 2 more95 min
Apr 9, 3:42 PM CDTSevere Thunderstorm WatchSPCEast Carroll, Franklin, Madison, Morehouse, Richland, Tensas and 1 more7 hr
Apr 9, 5:19 PM CDTMesoscale DiscussionSPCBienville, Caldwell, Claiborne, De Soto, Franklin, Grant and 10 more116 min
Apr 9, 6:14 PM CDTMesoscale DiscussionSPCCaldwell, East Carroll, Franklin, Madison, Morehouse, Ouachita and 2 more3 hr
Apr 8, 9:58 PM CDTMesoscale DiscussionSPCAnderson, Brazos, Cherokee, Freestone, Grimes, Henderson and 7 more2 hr
Apr 9, 3:14 PM CDTMesoscale DiscussionSPCCooke, Delta, Fannin, Grayson, Lamar, Montague and 1 more61 min
Apr 9, 3:59 PM CDTMesoscale DiscussionSPCBastrop, Bell, Blanco, Bosque, Burnet, Caldwell and 14 more2 hr
Apr 9, 4:27 PM CDTSevere Thunderstorm WatchSPCAnderson, Bell, Bosque, Collin, Cooke, Coryell and 26 more9 hr

Nearby

Severe Thunderstorm Watches in Texas, 2021Severe Thunderstorm Watches in Louisiana, 2021Every severe thunderstorm watch 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.