Alert archive / Louisiana / Mesoscale Discussions in 2016

Mesoscale Discussion 976

June 18, 201617 parishes in Louisiana; 14 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Jun 18, 2016, 11:31 AM CDT for 17 parishes in Louisiana; 14 counties in Texas. It was in force for 89 min.

The area

The outline as issued.

The facts

Issued: Jun 18, 2016, 11:31 AM CDT (16:31 UTC)
Expired: Jun 18, 2016, 1:00 PM CDT
In force: 89 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

All 31 counties

Acadia Parish, LA, Allen Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, De Soto Parish, LA, Evangeline Parish, LA, Jefferson Davis Parish, LA, Lafayette Parish, LA, Natchitoches Parish, LA, Rapides Parish, LA, Red River Parish, LA, Sabine Parish, LA, Saint Landry Parish, LA, St. Mary Parish, LA, Vermilion Parish, LA, Vernon Parish, LA, Angelina County, TX, Hardin County, TX, Jasper County, TX, Jefferson County, TX, Nacogdoches County, TX, Newton County, TX, Orange County, TX, Panola County, TX, Polk County, TX, Sabine County, TX, San Augustine County, TX, Shelby County, TX, Trinity County, TX, Tyler County, TX

The radar

The Ft Polk radar (KPOE), 93 km from the middle of the area, began a volume at 16:30 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 watches that followed

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

Severe Thunderstorm Watch 270Jun 18, 1:15 PM CDT

The nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 12:00Z, 4.5 hours before the alert went out and 115 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: 2313 J/kg
Mixed-layer CIN: -44 J/kg
Mixed-layer LCL: 781 m above ground
0-6 km bulk shear: 21 kt
0-1 km storm-relative helicity: -57 m²/s²
0-3 km storm-relative helicity: 11 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

262 
ACUS11 KWNS 181632
SWOMCD
SPC MCD 181631 
LAZ000-TXZ000-181800-

MESOSCALE DISCUSSION 0976
NWS STORM PREDICTION CENTER NORMAN OK
1131 AM CDT SAT JUN 18 2016

AREAS AFFECTED...WRN AND SWRN LA / E TX

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 181631Z - 181800Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...STRONG TO LOW-END SEVERE GUSTS ARE POSSIBLE THIS
AFTERNOON.  CONVECTIVE TRENDS WILL BE MONITORED FOR THE POSSIBLE
NEED FOR A SEVERE THUNDERSTORM WATCH.

DISCUSSION...RADAR MOSAIC SHOWS A SEMI-ORGANIZED LOOSE CLUSTER OF
STORMS WITH AN ELONGATED COLD POOL/GUST FRONT ORIENTED FROM 40 MI E
OF SHV EXTENDING SEWD TO 20 MI W OF HUM NEAR THE MOUTH OF THE
ATCHAFALAYA.  SURFACE OBSERVATIONS AHEAD OF THE TSTM BAND HAVE
WARMED INTO THE MID-UPPER 80S WITH MID 70S DEWPOINTS.  THE 12Z LCH
RAOB SHOWED A PRONOUNCED COLD POCKET AT H5 /-11.5 DEG C/ AND A VERY
UNSTABLE BOUNDARY LAYER IS IN PLACE AHEAD OF THE TSTM COMPLEX AS
SAMPLED BY THE 12Z SHV-LCH RAOBS WHEN MODIFIED FOR CURRENT SURFACE
CONDITIONS /2000-3000 J PER KG MLCAPE/.

ALTHOUGH THE WINDS THROUGH THE TROPOSPHERE WILL REMAIN WEAK...H5-H2
FLOW OF 20-30 KT FROM THE NNE ATOP WEAK WLY/S AT THE SURFACE WILL
PROMOTE A SWWD PROPAGATION OF THE TSTM BAND INTO THE SABINE RIVER
VALLEY LATER THIS AFTERNOON.  SMALL TO MARGINALLY SEVERE HAIL MAY
ACCOMPANY THE STRONGEST UPDRAFTS GIVEN THE COOL MID-LEVEL TEMPS BUT
ISOLD DOWNDRAFTS CAPABLE OF WIND DAMAGE OWING TO 50-60 MPH WINDS
APPEAR TO BE THE PRIMARY RISK.

..SMITH/GUYER.. 06/18/2016

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

ATTN...WFO...LCH...SHV...HGX...

LAT...LON   29809432 30939548 31969499 32379395 32159318 29609121
            29809432

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jun 18, 1:16 PM CDT	Severe Thunderstorm Watch	SPC	Acadia, Allen, Beauregard, Bossier, Caddo, Calcasieu and 11 more	6 hr
Jun 18, 3:20 PM CDT	Mesoscale Discussion	SPC	Beauregard, Calcasieu, Cameron, Jefferson Davis	25 min
Jun 18, 3:14 PM CDT	Mesoscale Discussion	SPC	Archer, Baylor, Clay, Foard, Hardeman, Montague and 2 more	2 hr

Nearby

Mesoscale Discussions in Louisiana, 2016 Mesoscale Discussions in Texas, 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; radar from the NEXRAD Level II archive.