Alert archive / Louisiana / Mesoscale Discussions in 2012

Mesoscale Discussion 452

April 5, 2012Ashley County, Chicot County, Arkansas; 27 parishes in Louisiana; 14 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Apr 5, 2012, 1:35 AM CDT for Ashley County, Chicot County, Arkansas; 27 parishes in Louisiana; 14 counties in Mississippi. It was in force for 85 min.

The area

The outline as issued.

The facts

Issued: Apr 5, 2012, 1:35 AM CDT (06:35 UTC)
Expired: Apr 5, 2012, 3:00 AM CDT
In force: 85 min
Issued by: the Storm Prediction Center

All 43 counties

Ashley County, AR, Chicot County, AR, Avoyelles Parish, LA, Caldwell Parish, LA, Catahoula Parish, LA, Concordia Parish, LA, East Baton Rouge Parish, LA, East Carroll Parish, LA, East Feliciana Parish, LA, Evangeline Parish, LA, Franklin Parish, LA, Grant Parish, LA, Jackson Parish, LA, LaSalle Parish, LA, Lincoln Parish, LA, Madison Parish, LA, Morehouse Parish, LA, Natchitoches Parish, LA, Ouachita Parish, LA, Pointe Coupee Parish, LA, Rapides Parish, LA, Richland Parish, LA, Saint Helena Parish, LA, Saint Landry Parish, LA, Tensas Parish, LA, Union Parish, LA, West Carroll Parish, LA, West Feliciana Parish, LA, Winn Parish, LA, Adams County, MS, Amite County, MS, Claiborne County, MS, Copiah County, MS, Franklin County, MS, Hinds County, MS, Issaquena County, MS, Jefferson County, MS, Lincoln County, MS, Pike County, MS, Sharkey County, MS, Warren County, MS, Washington County, MS, Wilkinson 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 00:00Z, 6.6 hours before the alert went out and 154 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: 140 J/kg
Mixed-layer CIN: -159 J/kg
Mixed-layer LCL: 1625 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: 1 m²/s²
0-3 km storm-relative helicity: 65 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.

377 
ACUS11 KWNS 050635
SWOMCD
SPC MCD 050635 
MSZ000-LAZ000-ARZ000-050800-

MESOSCALE DISCUSSION 0452
NWS STORM PREDICTION CENTER NORMAN OK
0135 AM CDT THU APR 05 2012

AREAS AFFECTED...PORTIONS SERN AR...WRN MS...CENTRAL/NRN LA.

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

VALID 050635Z - 050800Z

POTENTIAL FOR SVR GUSTS...HAIL AND PERHAPS A TORNADO EXISTS WITH
ISOLATED SUPERCELL MOVING EWD FROM CENTRAL LA TOWARD SWRN MS. 
ACTIVITY FARTHER N NEAR AR BORDER APPEARS TO BE ROOTED IN ELEVATED
LAYER OF INFLOW...AND POSES PREDOMINANT HAIL RISK.

SFC MESOANALYSIS SHOWS RESIDUAL/EWD-DRIFTING SFC FRONTAL ZONE FROM
SERN AR SWWD ACROSS EXTREME W-CENTRAL LA...CLOSE TO BKN BAND OF
TSTMS THAT HAS DEVELOPED OVER THAT CORRIDOR.  FRONT BECOMES DIFFUSE
FARTHER SW ACROSS SE TX WITHIN AIR MASS AFFECTED BY OUTFLOW FROM
COASTAL/DAYTIME MCS.  SUBTLE THETAE GRADIENT WAS EVIDENT
INTERSECTING FRONTAL ZONE OVER W-CENTRAL LA NEAR POE...AND EXTENDING
ESEWD ACROSS CENTRAL LA NEAR AVOYELLES PARISH SUPERCELL...TO BETWEEN
BTR-MCB.  AIR MASS ALONG AND S OF THIS BOUNDARY CONTAINED RELATIVELY
MAXIMIZED LOW-LEVEL CAPE AND DEEP BUOYANCY.  UPPER 60S TO LOW 70S F
SFC DEW POINTS AND STEEP MIDLEVEL LAPSE RATES CONTRIBUTE TO MLCAPE
1500-2500 J/KG.  DEEP-LAYER SHEAR INCREASES WITH SWD EXTENT ACROSS
AREA...WITH EFFECTIVE SHEAR MAGNITUDES RANGING FROM ABOUT 50 KT SRN
LA TO 25 KT SRN AR.  LOW-LEVEL SRH APPEARS WEAK AREA-WIDE DUE TO
WEAK BOUNDARY-LAYER WINDS...THOUGH VORTICITY MAY BE MAXIMIZED NEAR
AFOREMENTIONED THETAE GRADIENT. FCST SOUNDINGS SUGGEST GRADUAL
INCREASE IN MLCINH EWD ACROSS SRN MS...BUT CORRIDOR OF FAVORABLE AIR
SHOULD EXTEND TO JUST W OF MCB.

..EDWARDS.. 04/05/2012

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

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

LAT...LON   31649343 33039244 33589142 33499085 33199069 32239044
            31299027 30589049 30449110 30589218 30769283 31649343

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 4, 8:31 PM CDT	Mesoscale Discussion	SPC	Calhoun, Clark, Columbia, Conway, Crawford, Dallas and 24 more	119 min
Apr 5, 1:53 AM CDT	Tornado Watch	SPC	Ashley, Chicot	9 hr
Apr 5, 3:30 AM CDT	Mesoscale Discussion	SPC	Ashley, Chicot, Union	2 hr
Apr 5, 7:36 AM CDT	Mesoscale Discussion	SPC	Chicot	54 min
Apr 5, 12:09 PM CDT	Mesoscale Discussion	SPC	Clay, Craighead, Crittenden, Greene, Mississippi, Randolph	96 min
Apr 5, 12:18 PM CDT	Severe Thunderstorm Watch	SPC	Crittenden, Mississippi	5 hr
Apr 4, 8:25 PM CDT	Mesoscale Discussion	SPC	Acadia, Allen, Ascension, Assumption, Beauregard, Calcasieu and 21 more	95 min
Apr 5, 3:56 AM CDT	Tornado Watch	SPC	Ascension, Assumption, East Baton Rouge, East Feliciana, Iberville, Jefferson and 16 more	6 hr
Apr 5, 9:14 AM CDT	Severe Thunderstorm Watch	SPC	Greene, Perry, Wayne	8 hr
Apr 5, 10:41 AM CDT	Mesoscale Discussion	SPC	Greene, Wayne	94 min
Apr 5, 10:43 AM CDT	Severe Thunderstorm Watch	SPC	Clarke, Covington, Forrest, Franklin, Jasper, Jefferson Davis and 7 more	4 hr
Apr 5, 2:22 PM CDT	Mesoscale Discussion	SPC	Alcorn, Benton, Calhoun, Chickasaw, DeSoto, Itawamba and 14 more	53 min

Nearby

Mesoscale Discussions in Louisiana, 2012 Mesoscale Discussions in Mississippi, 2012 Mesoscale Discussions in Arkansas, 2012 Every 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.