Alert archive / Louisiana / Mesoscale Discussions in 2016

Mesoscale Discussion 362

April 11, 201618 parishes in Louisiana; 17 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Apr 11, 2016, 12:15 PM CDT for 18 parishes in Louisiana; 17 counties in Mississippi. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Apr 11, 2016, 12:15 PM CDT (17:15 UTC)
Expired: Apr 11, 2016, 2:45 PM CDT
In force: 3 hr
Issued by: the Storm Prediction Center
Chance of a watch: 40%

All 35 counties

Allen Parish, LA, Avoyelles Parish, LA, Catahoula Parish, LA, Concordia Parish, LA, East Feliciana Parish, LA, Evangeline Parish, LA, Grant Parish, LA, LaSalle Parish, LA, Natchitoches Parish, LA, Pointe Coupee Parish, LA, Rapides Parish, LA, Saint Helena Parish, LA, Saint Landry Parish, LA, Tensas Parish, LA, Vernon Parish, LA, Washington Parish, LA, West Feliciana Parish, LA, Winn Parish, LA, Adams County, MS, Amite County, MS, Claiborne 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, Simpson County, MS, Smith County, MS, Walthall County, MS, Wilkinson County, MS

The watches that followed

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

Severe Thunderstorm Watch 84Apr 11, 1:05 PM CDT

The nearest sounding before it

Jackson, MS (KJAN), launched 12:00Z, 5.3 hours before the alert went out and 172 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 807 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: 303 m²/s²
0-3 km storm-relative helicity: 445 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

007 
ACUS11 KWNS 111716
SWOMCD
SPC MCD 111715 
MSZ000-LAZ000-111945-

MESOSCALE DISCUSSION 0362
NWS STORM PREDICTION CENTER NORMAN OK
1215 PM CDT MON APR 11 2016

AREAS AFFECTED...PORTIONS OF CNTRL/SRN/ERN LA...CNTRL/SRN MS

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 111715Z - 111945Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...THE AREA IS BEING MONITORED FOR A POSSIBLE INCREASE IN
SVR-TSTM POTENTIAL. IT IS POSSIBLE THAT THIS COULD WARRANT WW
ISSUANCE THIS AFTERNOON.

DISCUSSION...ISOLATED TO WIDELY SCATTERED CONVECTION FROM PARTS OF
THE LOWER SABINE VALLEY TO SWRN MS HAS SHOWN SIGNS OF
INTENSIFICATION THROUGH LATE MORNING/EARLY AFTERNOON. THIS ACTIVITY
LIES WITHIN A WEAKLY DEFINED WARM-CONVEYOR STRUCTURE RELATED TO A
MID-LEVEL IMPULSE CROSSING THE ARKLATEX REGION. FORCING FOR ASCENT
ACROSS THE REGION WILL REMAIN QUITE LIMITED -- S OF LOCATIONS
ADDRESSED IN RECENTLY ISSUED MCD 0361. NEVERTHELESS...THE
COMBINATION OF LIMITED SFC HEATING AND MODEST ASCENT COULD BE
SUFFICIENT FOR FURTHER DEEPENING OF CONVECTION INTO THE AFTERNOON
HOURS AS MLCAPE INCREASES TO 1000-2000 J/KG. AMPLE DEEP SHEAR
OFFERED BY AROUND 40-50 KT OF WSWLY MID-LEVEL FLOW SAMPLED BY THE
POE VWP WILL BE SUFFICIENT FOR ORGANIZED CONVECTIVE STRUCTURES
/POSSIBLE SUPERCELLS/ WITH SVR HAIL/WIND. FURTHERMORE...SUFFICIENT
LOW-LEVEL SHEAR ASSOCIATED WITH A VERTICALLY VEERING WIND PROFILE
WILL SUPPORT SOME TORNADO RISK. HOWEVER...ANTECEDENT CAPPING IN THE
850-700-MB LAYER SAMPLED BY THE 12Z SHV AND LCH RAOBS DETRACTS
CONFIDENCE IN SUSTAINED...DEEP...ROTATING CONVECTION
OCCURRING...ESPECIALLY GIVEN WIDESPREAD CLOUD COVERAGE IN THE
PRE-CONVECTIVE AIR LIMITING LOW-LEVEL LAPSE RATES...AND ONLY WEAK
ASCENT. NEVERTHELESS...THE AREA WILL CONTINUE TO BE MONITORED FOR
SOME SVR RISK THROUGH THE AFTERNOON.

..COHEN/GOSS.. 04/11/2016

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

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

LAT...LON   30369258 31089336 31969325 32019120 32318961 31478910
            30868996 30369258

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 11, 11:48 AM CDT	Mesoscale Discussion	SPC	Bienville, Bossier, Caddo, Claiborne, East Carroll, Franklin and 9 more	2 hr
Apr 11, 1:05 PM CDT	Severe Thunderstorm Watch	SPC	Allen, Avoyelles, Beauregard, Bienville, Bossier, Caddo and 31 more	6 hr
Apr 11, 3:42 PM CDT	Mesoscale Discussion	SPC	Allen, Avoyelles, Bienville, Caldwell, Catahoula, Claiborne and 25 more	93 min
Apr 11, 6:09 PM CDT	Mesoscale Discussion	SPC	Avoyelles, Bienville, Caldwell, Catahoula, Claiborne, Concordia and 23 more	66 min
Apr 11, 6:58 PM CDT	Severe Thunderstorm Watch	SPC	Bienville, Bossier, Caddo, Caldwell, Catahoula, Claiborne and 20 more	5 hr
Apr 11, 6:40 PM CDT	Mesoscale Discussion	SPC	Clarke, Covington, Forrest, Greene, Jones, Lamar and 2 more	65 min

Nearby

Mesoscale Discussions in Louisiana, 2016 Mesoscale Discussions in Mississippi, 2016 Every mesoscale discussion in 2016

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.