Alert archive / Louisiana / Mesoscale Discussions in 2020

Mesoscale Discussion 399

April 18, 202032 parishes in Louisiana; 7 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Apr 18, 2020, 8:56 PM CDT for 32 parishes in Louisiana; 7 counties in Mississippi. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Apr 18, 2020, 8:56 PM CDT (01:56 UTC)
Expired
Apr 18, 2020, 11:00 PM CDT
In force
2 hr
Issued by
the Storm Prediction Center
Chance of a watch
5%
All 39 counties

Acadia Parish, LA, Allen Parish, LA, Ascension Parish, LA, Assumption Parish, LA, Cameron Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Evangeline Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Davis Parish, LA, Jefferson Parish, LA, Lafayette Parish, LA, Lafourche Parish, LA, Livingston Parish, LA, Orleans 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 Landry Parish, LA, Saint Martin Parish, LA, Saint Tammany Parish, LA, St. Mary Parish, LA, Tangipahoa Parish, LA, Terrebonne Parish, LA, Vermilion Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Amite County, MS, Hancock County, MS, Harrison County, MS, Pearl River County, MS, Pike County, MS, Walthall County, MS, Wilkinson County, MS

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 00:00Z, 1.9 hours before the alert went out and 112 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, Slidell Radar S, LA at 00:00Z on 2020-04-19Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 514 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, Slidell Radar S, LA at 00:00Z on 2020-04-19The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 20 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
514 J/kg
Mixed-layer CIN
-29 J/kg
Mixed-layer LCL
570 m above ground
0-6 km bulk shear
66 kt
0-1 km storm-relative helicity
20 m²/s²
0-3 km storm-relative helicity
92 m²/s²
Significant tornado parameter
0.4
Supercell composite
1.9

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 18, 8:27 PM CDTMesoscale DiscussionSPCBienville, Bossier, Caddo, Claiborne, De Soto, Red River and 1 more2 hr
Apr 19, 8:41 AM CDTTornado WatchSPCAllen, Beauregard, Bienville, Bossier, Caddo, Calcasieu and 18 more6 hr
Apr 19, 10:45 AM CDTMesoscale DiscussionSPCCaldwell, De Soto, Grant, Jackson, LaSalle, Natchitoches and 5 more2 hr
Apr 19, 11:06 AM CDTMesoscale DiscussionSPCAvoyelles, Catahoula, Concordia, Franklin, Madison, Richland and 1 more54 min
Apr 19, 11:45 AM CDTTornado WatchSPCCatahoula, Concordia, East Carroll, Franklin, Madison, Morehouse and 3 more9 hr
Apr 19, 12:39 PM CDTMesoscale DiscussionSPCBeauregard, Calcasieu, Vernon66 min
Apr 19, 12:47 PM CDTMesoscale DiscussionSPCAvoyelles, Bienville, Caldwell, Catahoula, Concordia, De Soto and 14 more58 min
Apr 19, 2:03 PM CDTMesoscale DiscussionSPCAcadia, Allen, Assumption, Avoyelles, Beauregard, Calcasieu and 23 more57 min
Apr 19, 2:39 PM CDTTornado WatchSPCAcadia, Allen, Ascension, Assumption, Avoyelles, Beauregard and 39 more9 hr
Apr 19, 3:07 PM CDTMesoscale DiscussionSPCMadison, Tensas113 min
Apr 19, 5:40 PM CDTMesoscale DiscussionSPCAcadia, Allen, Avoyelles, Beauregard, Calcasieu, Catahoula and 18 more2 hr
Apr 19, 6:37 PM CDTMesoscale DiscussionSPCWashington53 min
Apr 19, 2:34 AM CDTMesoscale DiscussionSPCAttala, Bolivar, Calhoun, Carroll, Chickasaw, Choctaw and 29 more116 min
Apr 19, 3:56 PM CDTTornado WatchSPCGeorge, Greene, Perry, Stone, Wayne6 hr

Nearby

Mesoscale Discussions in Louisiana, 2020Mesoscale Discussions in Mississippi, 2020Every mesoscale discussion in 2020

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.