Alert archive / Louisiana / Mesoscale Discussions in 2016

Mesoscale Discussion 508

April 29, 20168 counties in Arkansas; 11 parishes in Louisiana; 10 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Apr 29, 2016, 11:42 PM CDT for 8 counties in Arkansas; 11 parishes in Louisiana; 10 counties in Texas. It was in force for 93 min.

The area

The outline as issued.

The facts

Issued
Apr 29, 2016, 11:42 PM CDT (04:42 UTC)
Expired
Apr 30, 2016, 1:15 AM CDT
In force
93 min
Issued by
the Storm Prediction Center
All 29 counties

Bradley County, AR, Columbia County, AR, Lafayette County, AR, Little River County, AR, Miller County, AR, Nevada County, AR, Ouachita County, AR, Union County, AR, Bienville Parish, LA, Bossier Parish, LA, Caddo Parish, LA, Claiborne Parish, LA, De Soto Parish, LA, Jackson Parish, LA, Lincoln Parish, LA, Ouachita Parish, LA, Red River Parish, LA, Union Parish, LA, Webster Parish, LA, Bowie County, TX, Camp County, TX, Cass County, TX, Gregg County, TX, Harrison County, TX, Marion County, TX, Morris County, TX, Panola County, TX, Rusk County, TX, Upshur County, TX

The radar

The Shreveport radar (KSHV), 46 km from the middle of the area, began a volume at 04:41 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 nearest sounding before it

Shreveport, LA (KBAD), launched 00:00Z, 4.7 hours before the alert went out and 37 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-pSkew-T log-p diagram, Shreveport, LA at 00:00Z on 2016-04-30Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 835 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Shreveport, LA at 00:00Z on 2016-04-30The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 455 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
835 J/kg
Mixed-layer CIN
-28 J/kg
Mixed-layer LCL
591 m above ground
0-6 km bulk shear
68 kt
0-1 km storm-relative helicity
455 m²/s²
0-3 km storm-relative helicity
577 m²/s²
Significant tornado parameter
2.9
Supercell composite
11.8

Open this sounding in Storm Lab

The text

As transmitted.

983 
ACUS11 KWNS 300442
SWOMCD
SPC MCD 300442 
LAZ000-ARZ000-TXZ000-300615-

MESOSCALE DISCUSSION 0508
NWS STORM PREDICTION CENTER NORMAN OK
1142 PM CDT FRI APR 29 2016

AREAS AFFECTED...ARKLATEX

CONCERNING...SEVERE THUNDERSTORM WATCH 127...128...

VALID 300442Z - 300615Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH
127...128...CONTINUES.

SUMMARY...THE RISK FOR STRONG SURFACE GUSTS AND PERHAPS ISOLATED
TORNADOES IS EXPECTED TO CONTINUE INTO THE 06-09Z TIME
FRAME...GRADUALLY SHIFTING EAST OF THE ARKLATEX /AND THE SHREVEPORT
AREA/.  AREAS EAST OF WATCH 128 WILL BE MONITORED FOR THE
POSSIBILITY OF AN ADDITIONAL WATCH.

DISCUSSION...A LARGE AREA OF THUNDERSTORM ACTIVITY
CONTINUES...ROUGHLY CENTERED ACROSS OR JUST TO THE SOUTHWEST OF THE
ARKLATEX REGION.  THIS APPEARS GENERALLY FOCUSED BENEATH STRONGEST
HIGH LEVEL DIVERGENCE...WITHIN A ZONE OF BROAD UPPER DIFLUENCE
EXTENDING EAST NORTHEASTWARD OUT OF THE LOWER RIO GRANDE VALLEY.  A
BROAD BELT OF 40-50 KT SOUTHERLY 850 MB FLOW ACROSS UPPER TEXAS AND
LOUISIANA COASTAL AREAS INTO THE OZARK PLATEAU IS ALSO ENHANCING
LOW-LEVEL WARM ADVECTION ACROSS THIS REGION.  IT APPEARS THAT THIS
MAY PERSIST ANOTHER SEVERAL HOURS...AT LEAST THROUGH THE 06-08Z TIME
FRAME.

SOUTHEASTERLY NEAR SURFACE FLOW TO THE NORTH OF A BOUNDARY GENERATED
BY PERSISTENT CONVECTION IS CONTRIBUTING TO VERY LARGE AND CLOCKWISE
CURVED LOW-LEVEL HODOGRAPHS ACROSS AND SOUTH THROUGH WEST OF THE
SHREVEPORT AREA.  THIS HAS BEEN SUFFICIENT TO SUPPORT OCCASIONAL
DEVELOPMENT AND INTENSIFICATION OF LOW-LEVEL MESOCYCLONES WITH THE
MORE DISCRETE STRONGER CORES ACROSS THE ARKLATEX DURING THE PAST
HOUR OR TWO.

AS THESE CELLS TRACK NORTHWARD ABOVE A SLIGHTLY COOLER AND MORE
STABLE BOUNDARY LAYER TO THE NORTH OF THE ARKANSAS/LOUISIANA
BORDER...POTENTIAL FOR TORNADOES SEEMS LIKELY TO DIMINISH. 
HOWEVER...IN CLOSER PROXIMITY TO THE CONVECTIVE BOUNDARY ACROSS
NORTHERN LOUISIANA...WHERE SURFACE TEMPERATURES ARE IN MID 70S AND
DEW POINTS AROUND 70F...POTENTIAL FOR BRIEF TORNADOES...OR AT LEAST
LOCALIZED STRONG SURFACE GUSTS MAY CONTINUE.  AS THE LOW-LEVEL JET
SHIFTS TOWARD THE MISSISSIPPI RIVER OVERNIGHT...THIS PROBABLY WILL
GRADUALLY SHIFT EAST OF THE SHREVEPORT AREA THROUGH 07-09Z.

..KERR.. 04/30/2016

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

ATTN...WFO...JAN...LZK...SHV...FWD...

LAT...LON   32049267 32249194 33459205 33749337 33719431 32869543
            32049472 31989377 32049267

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 29, 8:56 PM CDTMesoscale DiscussionSPCBradley, Calhoun, Columbia, Hempstead, Lafayette, Little River and 4 more94 min
Apr 29, 9:58 PM CDTSevere Thunderstorm WatchSPCColumbia, Hempstead, Howard, Lafayette, Little River, Miller and 3 more7 hr
Apr 30, 3:23 AM CDTMesoscale DiscussionSPCCalhoun, Union97 min
Apr 30, 3:02 PM CDTMesoscale DiscussionSPCBaxter, Boone, Conway, Johnson, Logan, Marion and 5 more118 min
Apr 30, 3:59 PM CDTSevere Thunderstorm WatchSPCBaxter, Boone, Cleburne, Conway, Faulkner, Fulton and 13 more6 hr
Apr 30, 5:11 AM CDTSevere Thunderstorm WatchSPCAcadia, Allen, Avoyelles, Beauregard, Bienville, Calcasieu and 22 more9 hr
Apr 30, 7:38 AM CDTMesoscale DiscussionSPCAcadia, Allen, Beauregard, Calcasieu, Cameron, Evangeline and 2 more67 min
Apr 30, 10:22 AM CDTMesoscale DiscussionSPCAcadia, Ascension, Assumption, Calcasieu, Cameron, East Baton Rouge and 16 more53 min
Apr 30, 11:38 AM CDTSevere Thunderstorm WatchSPCAscension, Assumption, East Baton Rouge, East Feliciana, Iberville, Jefferson and 16 more7 hr
Apr 30, 1:35 PM CDTMesoscale DiscussionSPCAscension, Assumption, East Baton Rouge, East Feliciana, Iberia, Iberville and 22 more55 min
Apr 30, 4:00 PM CDTMesoscale DiscussionSPCAscension, Assumption, Jefferson, Lafourche, Livingston, Orleans and 10 more2 hr
Apr 29, 8:07 PM CDTMesoscale DiscussionSPCBandera, Bastrop, Bell, Bexar, Blanco, Bosque and 29 more83 min
Apr 29, 8:20 PM CDTSevere Thunderstorm WatchSPCBandera, Bastrop, Bexar, Blanco, Burnet, Caldwell and 19 more9 hr
Apr 30, 1:46 AM CDTMesoscale DiscussionSPCBandera, Bexar, Blanco, Comal, Hays, Kendall and 3 more59 min
Apr 30, 5:12 AM CDTMesoscale DiscussionSPCAustin, Burleson, Colorado, Fayette, Grimes, Harris and 7 more93 min
Apr 30, 5:27 AM CDTSevere Thunderstorm WatchSPCAustin, Brazoria, Brazos, Burleson, Chambers, Colorado and 11 more6 hr

Nearby

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