Alert archive / Mississippi / Mesoscale Discussions in 2012

Mesoscale Discussion 26

January 17, 201211 parishes in Louisiana; 14 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Jan 17, 2012, 3:45 PM CST for 11 parishes in Louisiana; 14 counties in Mississippi. It was in force for 60 min.

The area

The outline as issued.

The facts

Issued: Jan 17, 2012, 3:45 PM CST (21:45 UTC)
Expired: Jan 17, 2012, 4:45 PM CST
In force: 60 min
Issued by: the Storm Prediction Center

All 25 counties

Allen Parish, LA, Avoyelles Parish, LA, Beauregard Parish, LA, Concordia Parish, LA, East Feliciana Parish, LA, Evangeline Parish, LA, Pointe Coupee Parish, LA, Rapides Parish, LA, Saint Helena Parish, LA, Saint Landry Parish, LA, West Feliciana Parish, LA, Adams County, MS, Amite County, MS, Copiah County, MS, Covington County, MS, Franklin County, MS, Jefferson County, MS, Jefferson Davis County, MS, Lamar County, MS, Lawrence County, MS, Lincoln County, MS, Marion County, MS, Pike County, MS, Walthall County, MS, Wilkinson County, MS

The nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 12:00Z, 9.8 hours before the alert went out and 182 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: 1296 J/kg
Mixed-layer CIN: -33 J/kg
Mixed-layer LCL: 458 m above ground
0-6 km bulk shear: 35 kt
0-1 km storm-relative helicity: 278 m²/s²
0-3 km storm-relative helicity: 300 m²/s²
Significant tornado parameter: 1.5
Supercell composite: 8.5

Open this sounding in Storm Lab

The text

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

122 
ACUS11 KWNS 172146
SWOMCD
SPC MCD 172145
MSZ000-LAZ000-172245-

MESOSCALE DISCUSSION 0026
NWS STORM PREDICTION CENTER NORMAN OK
0345 PM CST TUE JAN 17 2012

AREAS AFFECTED...PARTS OF CENTRAL/SRN LA AND SRN MS

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 172145Z - 172245Z

THE POTENTIAL FOR ISOLATED STRONG TO SEVERE STORMS WILL PERSIST
ACROSS THE LOWER MS VALLEY /CENTRAL AND SRN LA TO SRN MS/ LATE THIS
AFTERNOON.  IN ADDITION TO SOME SEVERE WEATHER THREAT...STORMS
DEVELOPING OVER CENTRAL/SWRN LA WILL TEND TO TRACK ENEWD INTO FAR
SRN MS WHERE STORMS ARE ALREADY IN PROGRESS.  HEAVIER RAINFALL RATES
WILL BE POSSIBLE WITH THESE TRAINING STORMS.

MID-AFTERNOON SURFACE ANALYSES SHOWED A COLD FRONT STEADILY
ADVANCING EWD THROUGH THE LOWER MS VALLEY AND TOWARD THE TX COAST.
STORMS OVER CENTRAL LA WERE LOCATED ALONG AND E OF THE FRONT...WHILE
THE STORMS OVER FAR SRN MS WERE LOCATED ALONG AN APPARENT
DIFFERENTIAL HEATING BOUNDARY.  DESPITE SURFACE DEWPOINTS IN THE 60S
AND STEEP MIDLEVEL LAPSE RATES...EXTENSIVE CLOUDINESS HAS CONTINUED
TO INHIBIT GREATER SURFACE HEATING AND THUS MAINTAINING WEAK
INSTABILITY /MLCAPE 500-1000 J PER KG/.  STRONG EFFECTIVE BULK SHEAR
/AROUND 50 KT/ IS SUPPORTIVE FOR ORGANIZED STORMS...BUT VEERED
PRE-FRONTAL LOW LEVEL WINDS WILL CONTINUE TO LIMIT CONVERGENCE AND
OVERALL TSTM COVERAGE.  GIVEN STEEP MIDLEVEL LAPSE RATES AND DEEP
LAYER SHEAR...HAIL AND STRONG WIND GUSTS WILL BE POSSIBLE WITH THE
MORE SUSTAINED UPDRAFTS.

CONCERN ALSO EXISTS FOR HEAVY RAINFALL RATES...AS STORMS TRAIN ENEWD
FROM CENTRAL LA THROUGH EXTREME SRN MS...WITH THE GREATEST THREAT
AREA EXTENDING WSW-ENE WITHIN A 30-40 MILE WIDE CORRIDOR FROM NRN
EVANGELINE PARISH LA TO LAMAR COUNTY MS.  PRECIPITABLE WATER VALUES
TO AROUND 1.5 INCH WILL SUPPORT THIS THREAT.

..PETERS.. 01/17/2012

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

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

LAT...LON   30619347 31479216 31879144 31919007 31468922 30938971
            30709100 30379241 30329316 30619347

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jan 17, 9:26 AM CST	Mesoscale Discussion	SPC	Avoyelles, Bienville, Caldwell, Catahoula, Concordia, De Soto and 14 more	34 min

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.