Alert archive / Louisiana / Mesoscale Discussions in 2012

Mesoscale Discussion 312

March 20, 20126 parishes in Louisiana; Newton County, Texas

The Storm Prediction Center issued this mesoscale discussion at Mar 20, 2012, 10:23 PM CDT for 6 parishes in Louisiana; Newton County, Texas. It was in force for 67 min.

The area

The outline as issued.

The facts

Issued
Mar 20, 2012, 10:23 PM CDT (03:23 UTC)
Expired
Mar 20, 2012, 11:30 PM CDT
In force
67 min
Issued by
the Storm Prediction Center

Counties Allen Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Jefferson Davis Parish, LA, Natchitoches Parish, LA, Vernon Parish, LA, Newton County, TX

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 00:00Z, 3.4 hours before the alert went out and 343 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 00:00Z on 2012-03-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 267 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 00:00Z on 2012-03-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 36 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
267 J/kg
Mixed-layer CIN
-21 J/kg
Mixed-layer LCL
1256 m above ground
0-6 km bulk shear
24 kt
0-1 km storm-relative helicity
36 m²/s²
0-3 km storm-relative helicity
145 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

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

568 
ACUS11 KWNS 210323
SWOMCD
SPC MCD 210323 
LAZ000-TXZ000-210430-

MESOSCALE DISCUSSION 0312
NWS STORM PREDICTION CENTER NORMAN OK
1023 PM CDT TUE MAR 20 2012

AREAS AFFECTED...SERN THROUGH WCNTRL LA

CONCERNING...TORNADO WATCH 94...

VALID 210323Z - 210430Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 94 CONTINUES.

THE THREAT FOR ISOLATED TORNADOES WILL PERSIST ACROSS WRN THROUGH
NCNTRL LA THE REMAINDER OF THE EVENING. IN ADDITION...VERY HEAVY
RAIN WITH RATES FROM 1-2 INCHES PER HOUR WILL REMAIN LIKELY. THE WW
IS SCHEDULED TO EXPIRE AT 05Z...SO A WW DECISION WILL BE MADE BY
0430Z.

STORMS CONTINUE TRAINING SOUTH TO NORTH ALONG A QUASISTATIONARY
BOUNDARY ACROSS WRN LA SUPPORTED BY MOIST 40-50 KT INFLOW AND SLY
DEEP LAYER WINDS PARALLEL TO THE BOUNDARY. THIS PATTERN WILL NOT
CHANGE MUCH THE NEXT FEW HOURS...BUT THERE MAY BE A TENDENCY FOR THE
0-1 KM SHEAR TO UNDERGO A SLOW BUT GRADUAL DECREASE AS THE LLJ
DEVELOPS NWD WITH TIME. WEAK INSTABILITY WILL CONTINUE TO LIMIT
COVERAGE OF ANY SEVERE EVENTS. NEVERTHELESS POTENTIAL WILL REMAIN
FOR A FEW STORMS EMBEDDED WITHIN THE LINE TO DEVELOP LOW LEVEL
ROTATION AND PRODUCE A TORNADO GIVEN SIZE OF 0-1 KM HODOGRAPHS AND
LOW LFCS. OTHERWISE...VERY HEAVY RAIN REMAINS LIKELY AS STORMS TRAIN
NWD WITHIN A MOIST ENVIRONMENT.

..DIAL.. 03/21/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...LCH...SHV...

LAT...LON   29869386 30899378 31549347 31989312 31949263 30869270
            29979277 29869386

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, 10:59 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, 9:25 AM CDTMesoscale DiscussionSPCAscension, Concordia, East Baton Rouge, East Carroll, East Feliciana, Franklin and 17 more95 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
Mar 21, 12:39 PM CDTMesoscale DiscussionSPCClay, Collin, Cooke, Denton, Grayson, Montague and 1 more2 hr

Nearby

Mesoscale Discussions in Louisiana, 2012Mesoscale Discussions in Texas, 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.