Alert archive / Mississippi / Mesoscale Discussions in 2012

Mesoscale Discussion 2145

December 9, 20125 parishes in Louisiana; 14 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Dec 9, 2012, 9:59 PM CST for 5 parishes in Louisiana; 14 counties in Mississippi. It was in force for 61 min.

The area

The outline as issued.

The facts

Issued: Dec 9, 2012, 9:59 PM CST (03:59 UTC)
Expired: Dec 9, 2012, 11:00 PM CST
In force: 61 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

Counties Concordia Parish, LA, East Carroll Parish, LA, Franklin Parish, LA, Madison Parish, LA, Tensas Parish, LA, Adams County, MS, Claiborne County, MS, Copiah County, MS, Hinds County, MS, Issaquena County, MS, Jefferson County, MS, Leake County, MS, Madison County, MS, Rankin County, MS, Scott County, MS, Sharkey County, MS, Simpson County, MS, Warren County, MS, Yazoo County, MS

The radar

The Jackson/Brandon,MS radar (KDGX), 78 km from the middle of the area, began a volume at 04:02 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 nearest sounding before it

Jackson, MS (KJAN), launched 00:00Z, 4.0 hours before the alert went out and 69 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: 804 J/kg
Mixed-layer CIN: -4 J/kg
Mixed-layer LCL: 712 m above ground
0-6 km bulk shear: 48 kt
0-1 km storm-relative helicity: 226 m²/s²
0-3 km storm-relative helicity: 257 m²/s²
Significant tornado parameter: 1.1
Supercell composite: 5.0

Open this sounding in Storm Lab

The text

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

626 
ACUS11 KWNS 100400
SWOMCD
SPC MCD 100359
MSZ000-LAZ000-100500-

MESOSCALE DISCUSSION 2145
NWS STORM PREDICTION CENTER NORMAN OK
0959 PM CST SUN DEC 09 2012

AREAS AFFECTED...EXTREME NERN LA THROUGH SCNTRL MS

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 100359Z - 100500Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...SQUALL LINE WILL LIKELY CONTINUE EWD THROUGH NERN LA AND
EVENTUALLY INTO WRN AND CNTRL MS THROUGH THE EARLY MORNING. PRIMARY
THREAT WITH THE LINE WILL BE ISOLATED STRONG TO LOCALLY DAMAGING
WIND GUSTS...ESPECIALLY ALONG THE NRN END. TRENDS ARE BEING
MONITORED FOR A POSSIBLE WW ISSUANCE...OR ANOTHER OPTION IS FOR A
FEW COUNTIES TO BE LOCALLY EXTENDED FARTHER EAST INTO EXISTING WW
FOR NERN LA AND WCNTRL MS.

DISCUSSION...NRN END OF SQUALL LINE EXTENDING FROM NERN LA SWWD
THROUGH SERN TX IS MOVING EAST AT AROUND 30-35 KT. EMBEDDED
ORGANIZED STRUCTURES CONTINUE TO BE OBSERVED INCLUDING A BOOK END
VORTEX OVER NERN LA. THE THERMODYNAMIC ENVIRONMENT EAST OF THE LINE
WILL LIKELY REMAIN FAVORABLE FOR STORMS TO CONTINUE TO FORWARD
PROPAGATE. THE 00Z RAOB FROM JACKSON MODIFIED FOR CURRENT SFC
CONDITIONS INDICATES MLCAPE NEAR 1000 J/KG WITH WEAK CONVECTIVE
INHIBITION. TENDENCY WILL BE FOR THE LLJ TO SHIFT NEWD THROUGH THE
TN VALLEY LEAVING MODEST SWLY LOW LEVEL FLOW OVER THE LOWER MS
VALLEY. HOWEVER...VERTICAL SHEAR THROUGH A DEEPER LAYER WILL REMAIN
SUFFICIENT FOR EMBEDDED ORGANIZED STORM STRUCTURES AS THE ACTIVITY
DEVELOPS EWD NEXT FEW HOURS.

..DIAL/EDWARDS.. 12/10/2012

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

ATTN...WFO...JAN...

LAT...LON   31919186 32849129 33088975 32568935 31808991 31429162
            31919186

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, 11:24 PM CST	Mesoscale Discussion	SPC	Caldwell, Catahoula, East Carroll, Franklin, Grant, LaSalle and 6 more	66 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 Mississippi, 2012 Mesoscale Discussions in Louisiana, 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.