Alert archive / Louisiana / Mesoscale Discussions in 2012

Mesoscale Discussion 424

April 2, 2012Iberia Parish, St. Mary Parish, Louisiana

The Storm Prediction Center issued this mesoscale discussion at Apr 2, 2012, 10:10 PM CDT for Iberia Parish, St. Mary Parish, Louisiana. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Apr 2, 2012, 10:10 PM CDT (03:10 UTC)
Expired: Apr 3, 2012, 1:15 AM CDT
In force: 3 hr
Issued by: the Storm Prediction Center

Counties Iberia Parish, LA, St. Mary Parish, LA

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 00:00Z, 3.2 hours before the alert went out and 121 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: 269 J/kg
Mixed-layer CIN: -210 J/kg
Mixed-layer LCL: 862 m above ground
0-6 km bulk shear: 29 kt
0-1 km storm-relative helicity: -109 m²/s²
0-3 km storm-relative helicity: -89 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.5

Open this sounding in Storm Lab

The text

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

067 
ACUS11 KWNS 030310
SWOMCD
SPC MCD 030310 
LAZ000-030615-

MESOSCALE DISCUSSION 0424
NWS STORM PREDICTION CENTER NORMAN OK
1010 PM CDT MON APR 02 2012

AREAS AFFECTED...SRN LA

CONCERNING...HEAVY RAINFALL 

VALID 030310Z - 030615Z

SLOW-MOVING/TRAINING CONVECTION SHOULD PERSIST THROUGH ABOUT 05-07Z
ACROSS SRN LA...WITH 1-2 INCH PER HOUR RAINFALL RATES POSSIBLE.

A TRAINING CONVECTION SCENARIO HAS EVOLVED ALONG A STALLED OUTFLOW
BOUNDARY ACROSS SRN LA.  STORM DEVELOPMENT ALONG THE BOUNDARY IS
BEING MAINTAINED BY AN INFLUX OF LOW 70S BOUNDARY LAYER DEWPOINTS ON
20-30 KT LOW-LEVEL FLOW ABOVE THE COLD POOL.  ADDITIONALLY...A WEAK
MIDLEVEL TROUGH IS PIVOTING NEWD OVER THE NW GULF/WRN LA...WHICH
WILL CONTRIBUTE TO WEAK BACKGROUND ASCENT OVER CENTRAL/SRN LA THE
NEXT FEW HOURS.  GIVEN THE E-W BOUNDARY ORIENTATION AND WIND
PROFILES FAVORING GENERAL EWD STORM MOTION AROUND 10 KT...EXPECT THE
RISK FOR LOCALLY HEAVY RAINFALL TO PERSIST FOR THE NEXT SEVERAL
HOURS...UNTIL THE INFLUENCE OF THE MIDLEVEL TROUGH SHIFTS N OF THE
OUTFLOW BOUNDARY.

..THOMPSON.. 04/03/2012

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

ATTN...WFO...LIX...LCH...

LAT...LON   29549018 29469115 29449176 29619200 29789192 29869123
            29889068 29929004 29798968 29608967 29549018

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 3, 1:42 PM CDT	Mesoscale Discussion	SPC	East Carroll, Madison, West Carroll	93 min
Apr 3, 1:46 PM CDT	Mesoscale Discussion	SPC	Caddo, De Soto	89 min
Apr 3, 2:22 PM CDT	Severe Thunderstorm Watch	SPC	Bienville, Caldwell, Catahoula, Claiborne, Concordia, East Carroll and 16 more	8 hr
Apr 3, 2:36 PM CDT	Tornado Watch	SPC	Bossier, Caddo, De Soto, Sabine	7 hr
Apr 3, 5:24 PM CDT	Mesoscale Discussion	SPC	Bienville, Caldwell, Catahoula, Claiborne, Concordia, East Carroll and 16 more	66 min
Apr 3, 6:53 PM CDT	Mesoscale Discussion	SPC	Bossier, Caddo, Claiborne, De Soto, Red River, Webster	67 min

Nearby

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.