Alert archive / Mississippi / Mesoscale Discussions in 2012

Mesoscale Discussion 316

March 21, 201223 parishes in Louisiana; 31 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Mar 21, 2012, 9:25 AM CDT for 23 parishes in Louisiana; 31 counties in Mississippi. It was in force for 95 min.

The area

The outline as issued.

The facts

Issued
Mar 21, 2012, 9:25 AM CDT (14:25 UTC)
Expired
Mar 21, 2012, 11:00 AM CDT
In force
95 min
Issued by
the Storm Prediction Center
All 54 counties

Ascension Parish, LA, Concordia Parish, LA, East Baton Rouge Parish, LA, East Carroll Parish, LA, East Feliciana Parish, LA, Franklin Parish, LA, Jefferson Parish, LA, Lafourche Parish, LA, Livingston Parish, LA, Madison Parish, LA, Orleans Parish, LA, Ouachita Parish, LA, Richland Parish, LA, Saint Charles Parish, LA, Saint Helena Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Tammany Parish, LA, Tangipahoa Parish, LA, Tensas Parish, LA, Washington Parish, LA, West Carroll Parish, LA, West Feliciana Parish, LA, Adams County, MS, Amite County, MS, Claiborne County, MS, Copiah County, MS, Covington County, MS, Forrest County, MS, Franklin County, MS, Hancock County, MS, Harrison County, MS, Hinds County, MS, Issaquena County, MS, Jefferson County, MS, Jefferson Davis County, MS, Jones County, MS, Lamar County, MS, Lawrence County, MS, Lincoln County, MS, Madison County, MS, Marion County, MS, Pearl River County, MS, Perry County, MS, Pike County, MS, Rankin County, MS, Sharkey County, MS, Simpson County, MS, Smith County, MS, Stone County, MS, Walthall County, MS, Warren County, MS, Wilkinson County, MS, Yazoo County, MS

The watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

The nearest sounding before it

Jackson, MS (KJAN), launched 12:00Z, 2.4 hours before the alert went out and 131 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, Jackson, MS at 12:00Z on 2012-03-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 143 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, Jackson, MS at 12:00Z on 2012-03-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 239 square meters per square second.193958Sfc1 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
143 J/kg
Mixed-layer CIN
-17 J/kg
Mixed-layer LCL
559 m above ground
0-6 km bulk shear
42 kt
0-1 km storm-relative helicity
239 m²/s²
0-3 km storm-relative helicity
239 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.8

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

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SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Mar 20, 8:02 PM CDTTornado WatchSPCBeauregard, Calcasieu, Cameron, Vernon4 hr
Mar 20, 10:23 PM CDTMesoscale DiscussionSPCAllen, Beauregard, Calcasieu, Jefferson Davis, Natchitoches, Vernon67 min
Mar 20, 10:59 PM CDTTornado WatchSPCAcadia, Allen, Beauregard, Bienville, Calcasieu, Caldwell and 17 more7 hr
Mar 21, 2:17 AM CDTMesoscale DiscussionSPCAcadia, Avoyelles, Caldwell, Catahoula, Concordia, Evangeline and 17 more118 min
Mar 21, 4:38 AM CDTMesoscale DiscussionSPCAscension, Assumption, Avoyelles, Catahoula, Concordia, East Baton Rouge and 19 more97 min
Mar 21, 5:04 AM CDTTornado WatchSPCAcadia, Ascension, Assumption, Avoyelles, Caldwell, Catahoula and 33 more7 hr
Mar 21, 7:48 AM CDTMesoscale DiscussionSPCAscension, Assumption, Avoyelles, East Baton Rouge, East Feliciana, Iberville and 10 more87 min
Mar 21, 10:07 AM CDTTornado WatchSPCAscension, East Carroll, East Feliciana, Franklin, Jefferson, Lafourche and 17 more8 hr
Mar 21, 12:19 PM CDTMesoscale DiscussionSPCJefferson, Lafourche, Orleans, Plaquemines, Saint Bernard, Saint Tammany and 1 more86 min
Mar 21, 3:47 PM CDTMesoscale DiscussionSPCSaint Bernard88 min
Mar 21, 5:40 PM CDTMesoscale DiscussionSPCOrleans, Plaquemines, Saint Bernard35 min
Mar 21, 6:02 PM CDTTornado WatchSPCPlaquemines, Saint Bernard9 hr

Nearby

Mesoscale Discussions in Mississippi, 2012Mesoscale Discussions in Louisiana, 2012Every mesoscale discussion in 2012

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.