Alert archive / Louisiana / Mesoscale Discussions in 2012

Mesoscale Discussion 442

April 3, 2012Union County, Arkansas; 10 parishes in Louisiana; 9 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Apr 3, 2012, 8:47 PM CDT for Union County, Arkansas; 10 parishes in Louisiana; 9 counties in Texas. It was in force for 58 min.

The area

The outline as issued.

The facts

Issued: Apr 3, 2012, 8:47 PM CDT (01:47 UTC)
Expired: Apr 3, 2012, 9:45 PM CDT
In force: 58 min
Issued by: the Storm Prediction Center

Counties Union County, AR, Bienville Parish, LA, Bossier Parish, LA, Caddo Parish, LA, Claiborne Parish, LA, De Soto Parish, LA, Lincoln Parish, LA, Red River Parish, LA, Sabine Parish, LA, Union Parish, LA, Webster Parish, LA, Angelina County, TX, Cherokee County, TX, Houston County, TX, Nacogdoches County, TX, Panola County, TX, Rusk County, TX, Sabine County, TX, San Augustine County, TX, Shelby County, TX

The radar

The Shreveport radar (KSHV), 25 km from the middle of the area, began a volume at 01:47 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The watches that followed

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

Severe Thunderstorm Watch 138Apr 3, 9:50 PM CDT

The nearest sounding before it

Shreveport, LA (KSHV), launched 00:00Z, 1.8 hours before the alert went out and 26 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: 2361 J/kg
Mixed-layer CIN: -9 J/kg
Mixed-layer LCL: 1056 m above ground
0-6 km bulk shear: 31 kt
0-1 km storm-relative helicity: 96 m²/s²
0-3 km storm-relative helicity: 156 m²/s²
Significant tornado parameter: 1.1
Supercell composite: 7.7

Open this sounding in Storm Lab

The text

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

002 
ACUS11 KWNS 040147
SWOMCD
SPC MCD 040147 
LAZ000-ARZ000-TXZ000-040245-

MESOSCALE DISCUSSION 0442
NWS STORM PREDICTION CENTER NORMAN OK
0847 PM CDT TUE APR 03 2012

AREAS AFFECTED...NRN LA...NERN TX...FAR SRN AR

CONCERNING...TORNADO WATCH 135...

VALID 040147Z - 040245Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 135 CONTINUES.

BOTH SEVERE THUNDERSTORM WATCH 134 AND TORNADO WATCH 135 ARE
SCHEDULED TO EXPIRE AT 03Z. PORTIONS OF THESE WATCHES MAY BE 
REPLACED BY A NEW SEVERE TSTM WATCH PRIOR TO 03Z.

AS OF 0140Z...LONG-LIVED QLCS EXTENDED FROM WRN AR INTO E-CNTRL TX
WITH AN EMBEDDED BOWING STRUCTURE ALONG THE AR/LA BORDER. OUTFLOW
FROM AN MCS OVER THE LOWER MS VALLEY HAS INTERSECTED WITH THE
OUTFLOW FROM THE QLCS INVOF SHV. WITH TEMPERATURES HOLDING IN THE
MIDDLE 60S ACROSS N-CNTRL/NERN LA INTO S-CNTRL/SERN AR...THE ONGOING
BOW WILL LIKELY WEAKEN WITH A DECREASING DAMAGING WIND THREAT AS IT
ENCOUNTERS AN INCREASINGLY STABLE BOUNDARY LAYER. ORIENTATION OF THE
LINE APPEARS TO BE TAKING ON A MORE W-E SHAPE INVOF THE OUTFLOW
BOUNDARIES. THIS MAY RESULT IN THE DAMAGING WIND THREAT BECOMING
CONFINED FARTHER S IN ERN TX/WRN LA...ALONG WITH HEAVY RAIN GIVEN PW
VALUES AROUND 1.5 IN.

..GRAMS.. 04/04/2012

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

ATTN...WFO...JAN...LZK...SHV...HGX...FWD...

LAT...LON   31089473 31389562 31979530 32529419 32699370 33369298
            33399262 33279197 33029190 31989294 31309376 31089473

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 3, 7:01 PM CDT	Mesoscale Discussion	SPC	Clark, Crawford, Franklin, Garland, Hempstead, Hot Spring and 15 more	59 min
Apr 3, 9:48 PM CDT	Severe Thunderstorm Watch	SPC	Acadia, Allen, Avoyelles, Beauregard, Bienville, Calcasieu and 23 more	8 hr
Apr 3, 11:24 PM CDT	Mesoscale Discussion	SPC	Allen, Avoyelles, East Baton Rouge, East Feliciana, Evangeline, Grant and 12 more	96 min
Apr 4, 2:29 AM CDT	Mesoscale Discussion	SPC	Acadia, Ascension, Assumption, Calcasieu, Cameron, Iberia and 18 more	91 min
Apr 3, 7:35 PM CDT	Severe Thunderstorm Watch	SPC	Austin, Bastrop, Brazos, Burleson, Colorado, Fayette and 13 more	7 hr
Apr 4, 12:19 PM CDT	Mesoscale Discussion	SPC	Aransas, Austin, Bee, Brazoria, Calhoun, Chambers and 25 more	86 min
Apr 4, 12:55 PM CDT	Severe Thunderstorm Watch	SPC	Aransas, Bee, Brazoria, Brooks, Calhoun, Cameron and 19 more	6 hr
Apr 4, 3:32 PM CDT	Mesoscale Discussion	SPC	Aransas, Brazoria, Calhoun, Galveston, Kleberg, Matagorda and 1 more	88 min

Nearby

Mesoscale Discussions in Louisiana, 2012 Mesoscale Discussions in Texas, 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; radar from the NEXRAD Level II archive.