Alert archive / Louisiana / Severe Thunderstorm Watches in 2021
Severe Thunderstorm Watch 94
The Storm Prediction Center issued this severe thunderstorm watch at Apr 13, 2021, 12:06 PM CDT for 16 parishes in Louisiana. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Apr 13, 2021, 12:06 PM CDT (17:06 UTC)
- Expired
- Apr 13, 2021, 6:00 PM CDT
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 60 kt
Counties Ascension Parish, LA, Assumption Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Parish, LA, Lafourche Parish, LA, Orleans Parish, LA, Plaquemines Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Martin Parish, LA, Saint Tammany Parish, LA, St. Mary Parish, LA, Terrebonne Parish, LA
What SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 10%
- One or more EF2 to EF5 tornadoes
- 2%
- Ten or more severe wind reports
- 40%
- One or more gusts of 65 knots or more
- 20%
- Ten or more severe hail reports
- 40%
- One or more hailstones of 2 inches or more
- 20%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
9 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 13, 12:14 PM CDT | Severe Thunderstorm Warning | LIX | Saint Tammany, Tangipahoa | 14 min |
| Apr 13, 12:27 PM CDT | Severe Thunderstorm Warning | LIX | Lafourche, Saint Charles | 11 min |
| Apr 13, 12:53 PM CDT | Flash Flood Warning | LCH | Iberia, Lafayette, Saint Martin, St. Mary, Vermilion | 6 hr |
| Apr 13, 1:44 PM CDT | Severe Thunderstorm Warning | LIX | Lafourche, Saint Charles, Terrebonne | 31 min |
| Apr 13, 1:54 PM CDT | Flash Flood Warning | LIX | Jefferson | 111 min |
| Apr 13, 2:07 PM CDT | Flash Flood Warning | LIX | Saint Charles | 83 min |
| Apr 13, 2:22 PM CDT | Severe Thunderstorm Warning | LIX | Jefferson, Lafourche | 38 min |
| Apr 13, 2:47 PM CDT | Flash Flood Warning | LCH | Iberia, Saint Martin, St. Mary | 4 hr |
| Apr 13, 3:45 PM CDT | Severe Thunderstorm Warning | LIX | Jefferson | 15 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, 5.1 hours before the alert went out and 74 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 1989 m above ground
- 0-6 km bulk shear
- 41 kt
- 0-1 km storm-relative helicity
- 70 m²/s²
- 0-3 km storm-relative helicity
- 88 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
244 WWUS20 KWNS 131703 SEL4 SPC WW 131703 LAZ000-CWZ000-132300- URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 94 NWS Storm Prediction Center Norman OK 1205 PM CDT Tue Apr 13 2021 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Southeast Louisiana Coastal Waters * Effective this Tuesday afternoon and evening from 1205 PM until 600 PM CDT. * Primary threats include... Scattered damaging wind gusts to 70 mph possible Scattered large hail events to 1.5 inches in diameter possible SUMMARY...Clusters of elevated storms from this morning will begin to evolve into more surface-based storms this afternoon while moving southeastward with an increasing threat for occasional damaging winds across southeast Louisiana, including the New Orleans area. Otherwise, large hail will continue to be a threat with the strongest storms through the afternoon. The severe thunderstorm watch area is approximately along and 75 statute miles east and west of a line from 40 miles northwest of New Orleans LA to 55 miles southwest of Boothville LA. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU4). 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. && AVIATION...A few severe thunderstorms with hail surface and aloft to 1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 550. Mean storm motion vector 30025. ...Thompson
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 13, 8:28 AM CDT | Mesoscale Discussion | SPC | Acadia, Allen, Ascension, Assumption, Avoyelles, East Baton Rouge and 11 more | 2 hr |
| Apr 13, 11:43 AM CDT | Mesoscale Discussion | SPC | Ascension, Assumption, East Baton Rouge, Iberia, Iberville, Jefferson and 16 more | 2 hr |
| Apr 13, 2:44 PM CDT | Mesoscale Discussion | SPC | Iberia, Jefferson, Lafourche, Plaquemines, St. Mary, Terrebonne and 1 more | 2 hr |
| Apr 13, 3:43 PM CDT | Mesoscale Discussion | SPC | De Soto | 2 hr |
Nearby
Severe 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.