Alert archive / Louisiana / Tornado Watches in 2021
Tornado Watch 35
The Storm Prediction Center issued this tornado watch at Mar 17, 2021, 2:38 PM CDT for 25 parishes in Louisiana; 8 counties in Mississippi. It was in force for 8 hr.
The area
The outline as issued.
The facts
- Issued
- Mar 17, 2021, 2:38 PM CDT (19:38 UTC)
- Expired
- Mar 17, 2021, 11:00 PM CDT
- In force
- 8 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 65 kt
All 33 counties
Ascension Parish, LA, Assumption Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Parish, LA, Lafourche Parish, LA, Livingston Parish, LA, Orleans Parish, LA, Plaquemines Parish, LA, Pointe Coupee Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint Helena Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Martin Parish, LA, Saint Tammany Parish, LA, St. Mary Parish, LA, Tangipahoa Parish, LA, Terrebonne Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Amite County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Pearl River County, MS, Pike County, MS, Walthall County, MS, Wilkinson County, MS
What SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 60%
- One or more EF2 to EF5 tornadoes
- 50%
- Ten or more severe wind reports
- 50%
- One or more gusts of 65 knots or more
- 40%
- Ten or more severe hail reports
- 30%
- One or more hailstones of 2 inches or more
- 30%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
10 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 17, 3:30 PM CDT | Tornado Warning | LIX | Pointe Coupee, West Feliciana | 45 min |
| Mar 17, 3:53 PM CDT | Severe Thunderstorm Warning | LCH | Iberia, Saint Martin, St. Mary | 52 min |
| Mar 17, 4:05 PM CDT | Severe Thunderstorm Warning | LIX | Ascension, Assumption, East Baton Rouge, Iberville, Livingston, Saint James and 1 more | 40 min |
| Mar 17, 4:08 PM CDT | Tornado Warning | LIX | Amite, Wilkinson | 22 min |
| Mar 17, 4:44 PM CDT | Severe Thunderstorm Warning | LIX | Ascension, East Baton Rouge, Iberville, Livingston, Saint Helena, Tangipahoa | 34 min |
| Mar 17, 5:40 PM CDT | Severe Thunderstorm Warning | LIX | Washington | 31 min |
| Mar 17, 6:21 PM CDT | Severe Thunderstorm Warning | LCH | Iberia, Saint Martin, St. Mary | 39 min |
| Mar 17, 6:27 PM CDT | Severe Thunderstorm Warning | LIX | Ascension, Assumption, Iberville, Lafourche, Saint James, Terrebonne | 63 min |
| Mar 17, 8:20 PM CDT | Severe Thunderstorm Warning | LIX | Hancock, Harrison, Pearl River | 26 min |
| Mar 17, 9:54 PM CDT | Severe Thunderstorm Warning | LIX | Harrison, Jackson | 51 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
Slidell Radar S, LA (KSIL), launched 12:00Z, 7.6 hours before the alert went out and 91 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
- 1786 J/kg
- Mixed-layer CIN
- -40 J/kg
- Mixed-layer LCL
- 644 m above ground
- 0-6 km bulk shear
- 44 kt
- 0-1 km storm-relative helicity
- 205 m²/s²
- 0-3 km storm-relative helicity
- 396 m²/s²
- Significant tornado parameter
- 2.0
- Supercell composite
- 9.9
The text
As transmitted.
270
WWUS20 KWNS 171936
SEL5
SPC WW 171936
LAZ000-MSZ000-CWZ000-180200-
URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 35
NWS Storm Prediction Center Norman OK
240 PM CDT Wed Mar 17 2021
The NWS Storm Prediction Center has issued a
* Tornado Watch for portions of
Southeast Louisiana
Southern Mississippi
Coastal Waters
* Effective this Wednesday afternoon and evening from 240 PM
until 900 PM CDT.
* Primary threats include...
A few tornadoes likely with a couple intense tornadoes possible
Scattered damaging winds and isolated significant gusts to 75
mph possible
Isolated very large hail events to 2 inches in diameter possible
SUMMARY...A mixed of discrete supercells and clusters will spread
east-northeast from southwest Louisiana into southeast Louisiana and
southern Mississippi. Strong tornadoes are possible.
The tornado watch area is approximately along and 60 statute miles
east and west of a line from 5 miles northeast of Mc Comb MS to 50
miles west southwest of Houma LA. For a complete depiction of the
watch see the associated watch outline update (WOUS64 KWNS WOU5).
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 29...WW 30...WW 31...WW
32...WW 33...WW 34...
AVIATION...Tornadoes and 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 550. Mean
storm motion vector 24035.
...GramsSPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 17, 1:32 AM CDT | Mesoscale Discussion | SPC | Bienville, Bossier, Caddo, Claiborne, De Soto, Jackson and 6 more | 118 min |
| Mar 17, 4:04 AM CDT | Mesoscale Discussion | SPC | Bossier, Caddo | 86 min |
| Mar 17, 4:37 AM CDT | Severe Thunderstorm Watch | SPC | Bossier, Caddo | 5 hr |
| Mar 17, 6:40 AM CDT | Mesoscale Discussion | SPC | Bossier, Caddo, Claiborne, Webster | 95 min |
| Mar 17, 8:43 AM CDT | Tornado Watch | SPC | Bienville, Bossier, Caddo, Claiborne, De Soto, Jackson and 8 more | 4 hr |
| 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, 12:15 PM CDT | Mesoscale Discussion | SPC | Caldwell, Catahoula, East Carroll, Franklin, Jackson, LaSalle and 9 more | 90 min |
| Mar 17, 12:57 PM CDT | Tornado Watch | SPC | Bienville, Caldwell, Catahoula, Concordia, East Carroll, Franklin and 15 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, 2:56 PM CDT | Mesoscale Discussion | SPC | Caldwell, Catahoula, Concordia, East Carroll, Franklin, Grant and 7 more | 94 min |
| Mar 17, 5:34 AM CDT | Mesoscale Discussion | SPC | Alcorn, Benton, Bolivar, Calhoun, Coahoma, DeSoto and 15 more | 86 min |
| Mar 17, 5:53 AM CDT | Tornado Watch | SPC | Alcorn, Benton, Bolivar, Calhoun, Chickasaw, Coahoma and 20 more | 7 hr |
| Mar 17, 7:38 AM CDT | Mesoscale Discussion | SPC | Alcorn, Benton, Coahoma, DeSoto, Itawamba, Lafayette and 11 more | 67 min |
| Mar 17, 10:56 AM CDT | Mesoscale Discussion | SPC | Attala, Choctaw, Clarke, Clay, Copiah, Covington and 26 more | 2 hr |
| Mar 17, 11:36 AM CDT | Tornado Watch | SPC | Attala, Choctaw, Clarke, Clay, Copiah, Covington and 28 more | 7 hr |
| Mar 17, 12:02 PM CDT | Mesoscale Discussion | SPC | Clarke, Jones, Wayne | 58 min |
| Mar 17, 1:19 PM CDT | Mesoscale Discussion | SPC | Jefferson Davis, Lawrence, Lincoln, Simpson, Smith | 86 min |
| Mar 17, 5:49 PM CDT | Mesoscale Discussion | SPC | Clarke, Covington, Forrest, George, Greene, Jasper and 13 more | 86 min |
| Mar 17, 6:09 PM CDT | Mesoscale Discussion | SPC | Alcorn, Benton, Bolivar, Calhoun, Carroll, Chickasaw and 25 more | 66 min |
| Mar 17, 6:48 PM CDT | Tornado Watch | SPC | Attala, Choctaw, Clarke, Clay, Covington, Forrest and 20 more | 8 hr |
Nearby
Tornado Watches in Louisiana, 2021Tornado Watches in Mississippi, 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.