Alert archive / Texas / Mesoscale Discussions in 2016

Mesoscale Discussion 472

April 27, 20165 parishes in Louisiana; 23 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Apr 27, 2016, 4:28 AM CDT for 5 parishes in Louisiana; 23 counties in Texas. It was in force for 92 min.

The area

The outline as issued.

The facts

Issued: Apr 27, 2016, 4:28 AM CDT (09:28 UTC)
Expired: Apr 27, 2016, 6:00 AM CDT
In force: 92 min
Issued by: the Storm Prediction Center

All 28 counties

Beauregard Parish, LA, Natchitoches Parish, LA, Red River Parish, LA, Sabine Parish, LA, Vernon Parish, LA, Angelina County, TX, Atascosa County, TX, Austin County, TX, Colorado County, TX, DeWitt County, TX, Fort Bend County, TX, Hardin County, TX, Harris County, TX, Jasper County, TX, Karnes County, TX, Lavaca County, TX, Liberty County, TX, Montgomery County, TX, Nacogdoches County, TX, Newton County, TX, Polk County, TX, Sabine County, TX, San Augustine County, TX, San Jacinto County, TX, Tyler County, TX, Walker County, TX, Waller County, TX, Wilson County, TX

The watches that followed

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

Severe Thunderstorm Watch 114Apr 27, 4:55 AM CDT

The nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 00:00Z, 9.5 hours before the alert went out and 286 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: 1519 J/kg
Mixed-layer CIN: -82 J/kg
Mixed-layer LCL: 858 m above ground
0-6 km bulk shear: 33 kt
0-1 km storm-relative helicity: -62 m²/s²
0-3 km storm-relative helicity: 12 m²/s²
Significant tornado parameter: -0.2
Supercell composite: -2.7

Open this sounding in Storm Lab

The text

As transmitted.

553 
ACUS11 KWNS 270928
SWOMCD
SPC MCD 270928 
LAZ000-TXZ000-271100-

MESOSCALE DISCUSSION 0472
NWS STORM PREDICTION CENTER NORMAN OK
0428 AM CDT WED APR 27 2016

AREAS AFFECTED...PORTIONS NRN/WRN LA...SE/S-CENTRAL TX.

CONCERNING...SEVERE THUNDERSTORM WATCH 113...

VALID 270928Z - 271100Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 113
CONTINUES.

SUMMARY...MOST OF WW 113 MAY BE CLEARED BEHIND LINE AND/OR ALLOWED
TO EXPIRE AS SCHEDULED.  MRGL SVR THREAT MAY STILL EXIST A COUPLE
HOURS BEYOND INITIAL WW WITH BOWING SEGMENTS ACROSS PORTIONS SE
TX...ACROSS TOLEDO BEND RESERVOIR REGION INTO WRN LA.  NEW WW DOES
NOT APPEAR LIKELY ATTM...GIVEN LIMITED COVERAGE AND MRGL NATURE OF
THREAT...HOWEVER LOCAL EXTENSION IS BEING DONE FOR SOME COUNTIES IN
PROJECTED PATH OF SE TX CONVECTION.

DISCUSSION...AS OF 915Z...TWO PRIMARY/WELL-ORGANIZED BOWING SEGMENTS
HAVE DISTILLED FROM EARLIER EXTENSIVE QLCS -- ONE APCHG OCH/LFK AND
ANOTHER APCHG UTS/CXO CORRIDOR.  EACH IS INTERACTING WITH...AND AT
LEAST PARTLY BEHIND...GUST FRONTS FROM EARLIER ACTIVITY.  SFC
MESOANALYSIS SHOWS 4-5 MB/2-HR PRESSURE RISES WITH THESE SEGMENTS. 
PRIND AREA OF 50+ KT INBOUND VELOCITIES APPARENT IN RADAR DATA
ATOP/ABOVE BOUNDARY LAYER CONTAINS CONSIDERABLE HORIZONTAL
MOMENTUM...BUT THAT COMBINATION OF CONTINUING/PRECONVECTIVE SFC
DIABATIC COOLING AND GUST-FRONT-INDUCED STABILIZATION FROM EARLIER
CONVECTION WILL SUBSTANTIALLY MITIGATE POTENTIAL FOR DOWNWARD
MOMENTUM TRANSFER.  THIS IS REFLECTED TO SOME EXTENT IN MODIFIED RAP
SOUNDINGS SHOWING INCREASING MLCINH WITH EWD EXTENT AWAY FROM THIS
CONVECTION...WITHIN FREE WARM SECTOR.  SRN SEGMENT PRODUCED SUB-SVR
GUSTS DURING PAST HOUR -- E.G. 43 AND 44 KT AT CLL AND 11R
RESPECTIVELY AND LESS AT SURROUNDING OBS SITES.  STILL...ISOLATED
DAMAGING GUSTS APCHG SVR LIMITS ARE POSSIBLE EWD FROM ONGOING BOWING
SEGMENTS AS LOCALIZED VERTICAL CIRCULATIONS PROPEL STG WINDS THROUGH
STABLE LAYER TO SFC.

THOUGH CONVECTION FARTHER W ACROSS S-CENTRAL TX IS WELL BEHIND SFC
GUST FRONT...ISOLATED HAIL NEAR SVR LIMITS STILL IS POSSIBLE.

..EDWARDS.. 04/27/2016

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

ATTN...WFO...LCH...SHV...HGX...CRP...EWX...

LAT...LON   29299729 30219597 30639595 30909591 30839572 30959524
            31269492 31789491 31669454 31889368 32409329 32139304
            31519299 30819316 30289362 29569559 28929712 28739810
            28769876 28859899 28969909 29049899 29119877 29139845
            29239785 29269753 29299729

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 26, 9:36 PM CDT	Mesoscale Discussion	SPC	Bossier, Caddo	114 min
Apr 26, 10:21 PM CDT	Severe Thunderstorm Watch	SPC	Bossier, Caddo, De Soto, Red River, Sabine, Webster	9 hr
Apr 27, 1:35 AM CDT	Mesoscale Discussion	SPC	Bienville, Bossier, Caddo, Claiborne, De Soto, Lincoln and 3 more	115 min
Apr 27, 4:56 AM CDT	Severe Thunderstorm Watch	SPC	Allen, Beauregard, Calcasieu, Cameron, De Soto, Evangeline and 9 more	5 hr
Apr 27, 7:30 AM CDT	Mesoscale Discussion	SPC	Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Caldwell and 19 more	2 hr
Apr 27, 7:54 AM CDT	Severe Thunderstorm Watch	SPC	Acadia, Ascension, Assumption, Avoyelles, Catahoula, Concordia and 29 more	7 hr
Apr 26, 8:52 PM CDT	Mesoscale Discussion	SPC	Bosque, Brown, Callahan, Clay, Coleman, Collin and 34 more	53 min

Nearby

Mesoscale Discussions in Texas, 2016 Mesoscale Discussions in Louisiana, 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.