Alert archive / Louisiana / Tornado Watches in 2021
Tornado Watch 28
The Storm Prediction Center issued this tornado watch at Mar 17, 2021, 8:43 AM CDT for Columbia County, Union County, Arkansas; 14 parishes in Louisiana; 5 counties in Texas. It was in force for 4 hr.
The area
The outline as issued.
The facts
- Issued
- Mar 17, 2021, 8:43 AM CDT (13:43 UTC)
- Expired
- Mar 17, 2021, 1:00 PM CDT
- In force
- 4 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 65 kt
All 21 counties
Columbia County, AR, Union County, AR, Bienville Parish, LA, Bossier Parish, LA, Caddo Parish, LA, Claiborne Parish, LA, De Soto Parish, LA, Jackson 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, Nacogdoches County, TX, Sabine County, TX, San Augustine County, TX, Shelby County, TX
The radar
The Shreveport radar (KSHV), 85 km from the middle of the area, began a volume at 13:47 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
- 50%
- One or more EF2 to EF5 tornadoes
- 20%
- Ten or more severe wind reports
- 70%
- One or more gusts of 65 knots or more
- 40%
- Ten or more severe hail reports
- 20%
- One or more hailstones of 2 inches or more
- 10%
- Six or more combined severe hail and wind reports
- 90%
Warnings issued inside it
2 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 17, 9:29 AM CDT | Severe Thunderstorm Warning | SHV | De Soto, Sabine | 61 min |
| Mar 17, 11:42 AM CDT | Severe Thunderstorm Warning | SHV | Angelina, Sabine, San Augustine | 48 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, 1.7 hours before the alert went out and 77 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
- 1417 J/kg
- Mixed-layer CIN
- -55 J/kg
- Mixed-layer LCL
- 682 m above ground
- 0-6 km bulk shear
- 56 kt
- 0-1 km storm-relative helicity
- 328 m²/s²
- 0-3 km storm-relative helicity
- 340 m²/s²
- Significant tornado parameter
- 2.7
- Supercell composite
- 14.5
The text
As transmitted.
985
WWUS20 KWNS 171338
SEL8
SPC WW 171338
ARZ000-LAZ000-TXZ000-171800-
URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 28
NWS Storm Prediction Center Norman OK
840 AM CDT Wed Mar 17 2021
The NWS Storm Prediction Center has issued a
* Tornado Watch for portions of
Southwest Arkansas
Northwest Louisiana
Far eastern Texas
* Effective this Wednesday morning and afternoon from 840 AM
until 100 PM CDT.
* Primary threats include...
A few tornadoes possible
Scattered damaging winds likely with isolated significant gusts
to 75 mph possible
Isolated large hail events to 1.5 inches in diameter possible
SUMMARY...A squall line across eastern TX should continue east
across parts of the Sabine Valley into Louisiana and southern
Arkansas through midday. Damaging wind gusts will be the main hazard
initially, but the tornado risk should increase later this morning.
The tornado watch area is approximately along and 45 statute miles
east and west of a line from 10 miles east of El Dorado AR to 55
miles southwest of Natchitoches LA. For a complete depiction of the
watch see the associated watch outline update (WOUS64 KWNS WOU8).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Tornado Watch means conditions are favorable for
tornadoes and 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.
&&
OTHER WATCH INFORMATION...CONTINUE...WW 25...WW 26...WW 27...
AVIATION...Tornadoes and a few severe thunderstorms with hail
surface and aloft to 1.5 inches. Extreme turbulence and surface wind
gusts to 65 knots. A few cumulonimbi with maximum tops to 500. Mean
storm motion vector 26035.
...GramsSPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 17, 12:45 AM CDT | Mesoscale Discussion | SPC | Benton, Washington | 90 min |
| Mar 17, 1:32 AM CDT | Mesoscale Discussion | SPC | Ashley, Bradley, Calhoun, Clark, Cleveland, Columbia and 27 more | 118 min |
| Mar 17, 4:04 AM CDT | Mesoscale Discussion | SPC | Columbia, Hempstead, Lafayette, Little River, Miller, Sevier | 86 min |
| Mar 17, 4:37 AM CDT | Severe Thunderstorm Watch | SPC | Hempstead, Howard, Lafayette, Little River, Miller, Nevada and 1 more | 5 hr |
| Mar 17, 5:34 AM CDT | Mesoscale Discussion | SPC | Arkansas, Crittenden, Cross, Desha, Lee, Lincoln and 3 more | 86 min |
| Mar 17, 5:53 AM CDT | Tornado Watch | SPC | Arkansas, Bradley, Cleveland, Crittenden, Desha, Drew and 8 more | 7 hr |
| Mar 17, 6:40 AM CDT | Mesoscale Discussion | SPC | Calhoun, Clark, Columbia, Crawford, Dallas, Franklin and 19 more | 95 min |
| Mar 17, 7:38 AM CDT | Mesoscale Discussion | SPC | Crittenden, Lee, Monroe, Phillips, St. Francis | 67 min |
| Mar 17, 7:47 AM CDT | Tornado Watch | SPC | Calhoun, Clark, Conway, Dallas, Faulkner, Garland and 15 more | 5 hr |
| Mar 17, 12:15 PM CDT | Mesoscale Discussion | SPC | Ashley, Chicot, Desha, Drew, Phillips | 90 min |
| Mar 17, 12:57 PM CDT | Tornado Watch | SPC | Ashley, Chicot, Lee, Phillips | 6 hr |
| Mar 17, 1:18 PM CDT | Mesoscale Discussion | SPC | Benton, Boone, Carroll, Clark, Crawford, Franklin and 22 more | 57 min |
| Mar 17, 2:00 PM CDT | Tornado Watch | SPC | Benton, Boone, Carroll, Crawford, Franklin, Johnson and 12 more | 7 hr |
| Mar 17, 2:56 PM CDT | Mesoscale Discussion | SPC | Ashley, Chicot, Desha, Drew | 94 min |
| Mar 17, 3:37 PM CDT | Mesoscale Discussion | SPC | Baxter, Benton, Boone, Carroll, Crawford, Franklin and 5 more | 83 min |
| Mar 17, 6:09 PM CDT | Mesoscale Discussion | SPC | Crittenden, Cross | 66 min |
| Mar 17, 11:35 AM CDT | Mesoscale Discussion | SPC | Allen, Beauregard, Bienville, Calcasieu, Cameron, De Soto and 8 more | 85 min |
| Mar 17, 11:53 AM CDT | Tornado Watch | SPC | Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 7 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 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
Tornado Watches in Louisiana, 2021Tornado Watches in Texas, 2021Tornado Watches in Arkansas, 2021Every tornado 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.