Alert archive / Louisiana / Mesoscale Discussions in 2013

Mesoscale Discussion 430

April 10, 201324 parishes in Louisiana; 6 counties in Mississippi; Newton County, Texas

The Storm Prediction Center issued this mesoscale discussion at Apr 10, 2013, 4:46 PM CDT for 24 parishes in Louisiana; 6 counties in Mississippi; Newton County, Texas. It was in force for 119 min.

The area

The outline as issued.

The facts

Issued: Apr 10, 2013, 4:46 PM CDT (21:46 UTC)
Expired: Apr 10, 2013, 6:45 PM CDT
In force: 119 min
Issued by: the Storm Prediction Center
Chance of a watch: 60%

All 31 counties

Allen Parish, LA, Avoyelles Parish, LA, Beauregard Parish, LA, Bienville Parish, LA, Caldwell Parish, LA, Catahoula Parish, LA, Concordia Parish, LA, East Carroll Parish, LA, Evangeline Parish, LA, Franklin Parish, LA, Grant Parish, LA, Jackson Parish, LA, LaSalle Parish, LA, Lincoln Parish, LA, Madison Parish, LA, Natchitoches Parish, LA, Ouachita Parish, LA, Rapides Parish, LA, Red River Parish, LA, Richland Parish, LA, Sabine Parish, LA, Tensas Parish, LA, Vernon Parish, LA, Winn Parish, LA, Adams County, MS, Claiborne County, MS, Issaquena County, MS, Jefferson County, MS, Warren County, MS, Wilkinson County, MS, Newton County, TX

The watches that followed

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

Tornado Watch 92Apr 10, 5:45 PM CDT

The nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 12:00Z, 9.8 hours before the alert went out and 152 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 1477 J/kg
Mixed-layer CIN: -131 J/kg
Mixed-layer LCL: 516 m above ground
0-6 km bulk shear: 27 kt
0-1 km storm-relative helicity: 115 m²/s²
0-3 km storm-relative helicity: 176 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 1.4

Open this sounding in Storm Lab

The text

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

388 
ACUS11 KWNS 102147
SWOMCD
SPC MCD 102146 
MSZ000-LAZ000-TXZ000-102345-

MESOSCALE DISCUSSION 0430
NWS STORM PREDICTION CENTER NORMAN OK
0446 PM CDT WED APR 10 2013

AREAS AFFECTED...NORTHERN/CENTRAL LA INTO WESTERN MS

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 102146Z - 102345Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...NEAR/AHEAD OF A COLD FRONT...AT LEAST AN ISOLATED SEVERE
POTENTIAL MAY INCREASE THROUGH LATE AFTERNOON/EARLY EVENING ACROSS
PORTIONS OF NORTHERN/CENTRAL LA INTO WESTERN MS. THIS INCLUDES
POTENTIAL FOR DAMAGING THUNDERSTORM WINDS AND A TORNADO OR
TWO...MONITORING FOR A WATCH.

DISCUSSION...PER RECENT VISIBLE SATELLITE IMAGERY /SINCE
2045Z/...BOUNDARY LAYER CU FIELD WITHIN THE WARM SECTOR APPEARS TO
BE DEEPENING ESPECIALLY ACROSS NORTH-CENTRAL/NORTHEAST LA INTO FAR
SOUTHWEST MS...INCLUDING AREAS 50-75 MILES EITHER SIDE OF I-20. THIS
IS AHEAD A COLD FRONT WHICH EXTENDS SOUTH-SOUTHWESTWARD FROM A
WEST-CENTRAL AR SURFACE LOW TO NEAR THE SHREVEPORT AREA INTO EXTREME
EASTERN TX AS OF 21Z. WITHIN THE WARM SECTOR...BOUNDARY LAYER CINH
NOW APPEARS NEGLIGIBLE AMID LOWER 80S SURFACE TEMPERATURES AND UPPER
60S OR NEAR 70F SURFACE DEWPOINTS. AS SUCH...IT IS POSSIBLE THAT
WARM SECTOR TSTM DEVELOPMENT MAY CONTINUE TO OCCUR WITH ADDITIONAL
DESTABILIZATION...ESPECIALLY GIVEN GRADUAL HEIGHT FALLS/STRONG
DIFFLUENCE ON THE SOUTHERN PERIPHERAL OF A PLAINS UPPER TROUGH.
COINCIDENT WITH THE ENTRANCE REGION OF A MODERATELY STRONG SOUTHERLY
LOW LEVEL JET...LOW-LEVEL/DEEP LAYER WILL SUPPORT WARM SECTOR
SUPERCELLS AS UPDRAFTS CONTINUE TO MATURE...WITH A MORE LINEAR MODE
NEAR THE COLD FRONT. THUNDERSTORM WIND GUSTS AND PERHAPS A TORNADO
OR TWO WILL BE POSSIBLE THIS EVENING...AND INCREASING TRENDS MAY
PROMPT A WATCH ISSUANCE.

..GUYER/CORFIDI.. 04/10/2013

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

ATTN...WFO...JAN...LIX...LCH...SHV...

LAT...LON   30229410 32679329 32789065 31069098 30229410

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 10, 5:42 PM CDT	Tornado Watch	SPC	Caldwell, Catahoula, Concordia, East Carroll, Franklin, Grant and 11 more	7 hr
Apr 9, 7:22 PM CDT	Mesoscale Discussion	SPC	Hemphill	2 hr
Apr 9, 7:28 PM CDT	Mesoscale Discussion	SPC	Callahan, Eastland, Jack, Palo Pinto, Shackelford, Stephens and 3 more	62 min
Apr 9, 8:51 PM CDT	Mesoscale Discussion	SPC	Archer, Baylor, Clay, Foard, Hardeman, Knox and 3 more	54 min
Apr 9, 9:01 PM CDT	Mesoscale Discussion	SPC	Cooke, Fannin, Grayson, Lamar	89 min
Apr 9, 11:27 PM CDT	Mesoscale Discussion	SPC	Archer, Baylor, Clay, Foard, Hardeman, Knox and 3 more	63 min
Apr 10, 5:32 AM CDT	Mesoscale Discussion	SPC	Hardeman, Wichita, Wilbarger	4 hr

Nearby

Mesoscale Discussions in Louisiana, 2013 Mesoscale Discussions in Mississippi, 2013 Mesoscale Discussions in Texas, 2013 Every mesoscale discussion in 2013

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.