Alert archive / Louisiana / Mesoscale Discussions in 2012

Mesoscale Discussion 2146

December 9, 201212 parishes in Louisiana; 7 counties in Mississippi; Jasper County, Newton County, Texas

The Storm Prediction Center issued this mesoscale discussion at Dec 9, 2012, 11:24 PM CST for 12 parishes in Louisiana; 7 counties in Mississippi; Jasper County, Newton County, Texas. It was in force for 66 min.

The area

The outline as issued.

The facts

Issued: Dec 9, 2012, 11:24 PM CST (05:24 UTC)
Expired: Dec 10, 2012, 12:30 AM CST
In force: 66 min
Issued by: the Storm Prediction Center

All 21 counties

Caldwell Parish, LA, Catahoula Parish, LA, East Carroll Parish, LA, Franklin Parish, LA, Grant Parish, LA, LaSalle Parish, LA, Madison Parish, LA, Rapides Parish, LA, Richland Parish, LA, Tensas Parish, LA, Vernon Parish, LA, Winn Parish, LA, Claiborne County, MS, Hinds County, MS, Humphreys County, MS, Issaquena County, MS, Sharkey County, MS, Warren County, MS, Yazoo County, MS, Jasper County, TX, Newton County, TX

The nearest sounding before it

Shreveport, LA (KSHV), launched 00:00Z, 5.4 hours before the alert went out and 160 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: 928 J/kg
Mixed-layer CIN: -8 J/kg
Mixed-layer LCL: 874 m above ground
0-6 km bulk shear: 61 kt
0-1 km storm-relative helicity: 161 m²/s²
0-3 km storm-relative helicity: 192 m²/s²
Significant tornado parameter: 1.0
Supercell composite: 3.3

Open this sounding in Storm Lab

The text

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

953 
ACUS11 KWNS 100524
SWOMCD
SPC MCD 100524 
MSZ000-LAZ000-ARZ000-TXZ000-100630-

MESOSCALE DISCUSSION 2146
NWS STORM PREDICTION CENTER NORMAN OK
1124 PM CST SUN DEC 09 2012

AREAS AFFECTED...SWRN THROUGH NERN LA INTO WCNTRL MS

CONCERNING...SEVERE THUNDERSTORM WATCH 678...

VALID 100524Z - 100630Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 678
CONTINUES.

SUMMARY...SEVERE THUNDERSTORM WATCH 678 WILL BE ALLOWED TO EXPIRE AT
06Z. THE PRIMARY...BUT LIMITED SEVERE THREAT IN THE MEANTIME WILL
EXIST WITH PORTION OF SQUALL LINE MOVING INTO WCNTRL MS.

DISCUSSION...SQUALL LINE EXTENDS FROM WCNTRL MS SWWD THROUGH SWRN
LA. THE MORE PROGRESSIVE PORTION OF THE LINE REMAINS ON NRN END OVER
WCNTRL MS. RADAR DATA FROM JACKSON STILL SHOW A FEW BOWING ELEMENTS.
AT LEAST A MODEST THREAT FOR ISOLATED DAMAGING WIND WILL PERSIST
NEXT HOUR OR TWO AS ACTIVITY FORWARD PROPAGATES THROUGH AN
ENVIRONMENT CHARACTERIZED BY 40-50 KT UNIDIRECTIONAL EFFECTIVE SHEAR
BUT MODEST INSTABILITY.

FARTHER SW ACROSS LA...THE SQUALL LINE HAS BECOME ORIENTED NEARLY
PARALLEL TO THE MEAN WIND...RESULTING IN LIMITED SEWD PROPAGATION
AND A MORE MARGINAL SEVERE THREAT.

..DIAL.. 12/10/2012

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

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

LAT...LON   30939435 32569165 33339087 33058988 32059040 30429388
            30939435

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Dec 9, 8:38 PM CST	Mesoscale Discussion	SPC	Beauregard, Bienville, Bossier, Caddo, Caldwell, Claiborne and 15 more	67 min
Dec 9, 9:59 PM CST	Mesoscale Discussion	SPC	Concordia, East Carroll, Franklin, Madison, Tensas	61 min
Dec 10, 4:07 AM CST	Mesoscale Discussion	SPC	Acadia, Allen, Ascension, Assumption, Avoyelles, Cameron and 23 more	113 min
Dec 10, 5:44 AM CST	Tornado Watch	SPC	Ascension, Assumption, East Baton Rouge, East Feliciana, Iberia, Iberville and 10 more	5 hr
Dec 10, 7:31 AM CST	Mesoscale Discussion	SPC	Ascension, Assumption, Iberia, Jefferson, Lafourche, Livingston and 11 more	119 min
Dec 10, 8:51 AM CST	Tornado Watch	SPC	Jefferson, Orleans, Plaquemines, Saint Bernard, Saint Charles, Saint John the Baptist and 1 more	6 hr
Dec 10, 10:24 AM CST	Mesoscale Discussion	SPC	Orleans	2 hr

Nearby

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