Alert archive / Arkansas / Mesoscale Discussions in 2011

Mesoscale Discussion 478

April 19, 201119 counties in Arkansas; McCurtain County, Oklahoma; 17 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Apr 19, 2011, 7:47 PM CDT for 19 counties in Arkansas; McCurtain County, Oklahoma; 17 counties in Texas. It was in force for 88 min.

The area

The outline as issued.

The facts

Issued
Apr 19, 2011, 7:47 PM CDT (00:47 UTC)
Expired
Apr 19, 2011, 9:15 PM CDT
In force
88 min
Issued by
the Storm Prediction Center
All 37 counties

Conway County, AR, Franklin County, AR, Howard County, AR, Johnson County, AR, Little River County, AR, Logan County, AR, Marion County, AR, Montgomery County, AR, Newton County, AR, Perry County, AR, Pike County, AR, Polk County, AR, Pope County, AR, Scott County, AR, Searcy County, AR, Sebastian County, AR, Sevier County, AR, Van Buren County, AR, Yell County, AR, McCurtain County, OK, Bowie County, TX, Camp County, TX, Cass County, TX, Delta County, TX, Franklin County, TX, Hopkins County, TX, Hunt County, TX, Kaufman County, TX, Lamar County, TX, Morris County, TX, Rains County, TX, Red River County, TX, Rockwall County, TX, Titus County, TX, Upshur County, TX, Van Zandt County, TX, Wood County, TX

The radar

The Western Arkansas radar (KSRX), 89 km from the middle of the area, began a volume at 00:48 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.

The nearest sounding before it

Shreveport, LA (KSHV), launched 00:00Z, 0.8 hours before the alert went out and 228 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 2011-04-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 2277 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 2011-04-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 127 square meters per square second.193958Sfc1 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
2277 J/kg
Mixed-layer CIN
-179 J/kg
Mixed-layer LCL
1895 m above ground
0-6 km bulk shear
41 kt
0-1 km storm-relative helicity
127 m²/s²
0-3 km storm-relative helicity
165 m²/s²
Significant tornado parameter
0.0
Supercell composite
4.6

Open this sounding in Storm Lab

The text

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

646 
ACUS11 KWNS 200048
SWOMCD
SPC MCD 200047
ARZ000-TXZ000-OKZ000-200215-

MESOSCALE DISCUSSION 0478
NWS STORM PREDICTION CENTER NORMAN OK
0747 PM CDT TUE APR 19 2011

AREAS AFFECTED...NERN TX...EXTREME SERN OK...WRN AND CNTRL AR

CONCERNING...TORNADO WATCH 155...

VALID 200047Z - 200215Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 155 CONTINUES.

THREAT FOR MAINLY ISOLATED LARGE HAIL...DAMAGING WIND AND PERHAPS A
COUPLE OF ISOLATED TORNADOES WILL PERSIST NEXT FEW HOURS FROM NERN
TX...EXTREME SERN OK INTO WRN AR. STORMS COULD DEVELOP A LITTLE
FARTHER SWD INTO EXTREME SRN AR.

COLD FRONT EXTENDS FROM SRN MO SWWD THROUGH NWRN AR...SERN OK INTO
N-CNTRL TX WHERE IT INTERSECTS DRYLINE EAST OF STEPHENVILLE. THE
DRYLINE EXTENDS SWD TO EAST OF DEL RIO. ISOLATED STORMS CONTINUE
DEVELOPING NEAR TRIPLE POINT AND NEWD ALONG AND AHEAD OF THE COLD
FRONT THROUGH WRN AND CNTRL AR. DEEP VERTICAL SHEAR FROM 35-40
KT...STEEP LAPSE RATES AND 3000+ MLCAPE REMAIN SUPPORTIVE OF
SUPERCELLS WITH VERY LARGE HAIL. ISOLATED TORNADOES REMAIN POSSIBLE
NEXT COUPLE HOURS...BUT MODEST 0-1 KM STORM RELATIVE HELICITY IS NOT
EXPECTED TO UNDERGO A SIGNIFICANT INCREASE GIVEN PRIMARY LOW LEVEL
JET STRENGTHENING WELL EAST OF THIS REGION. THIS IN CONJUNCTION WITH
A STABILIZING BOUNDARY LAYER SHOULD REMAIN LIMITING FACTORS FOR A
MORE ROBUST TORNADO THREAT IN WW 155.

OVERALL COVERAGE OF STORMS IN NERN TX HAS DIMINISHED...BUT STORMS
MAY CONTINUE DEVELOPING SWD ALONG THE DRYLINE-COLD FRONT MERGER.
STORMS MAY ALSO BE MORE PERSISTENT ACROSS AR WHERE INFLUENCE OF
DEEPER ASCENT ATTENDING SHORTWAVE TROUGH APPEARS TO BE WEAKENING THE
CAPPING INVERSION.

..DIAL.. 04/20/2011

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

ATTN...WFO...LZK...SHV...TSA...FWD...

LAT...LON   34749478 36169335 36379266 36039202 34689312 33019422
            32439540 32389708 34749478

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 19, 8:07 PM CDTMesoscale DiscussionSPCArkansas, Clay, Cleveland, Craighead, Crittenden, Cross and 18 more83 min
Apr 19, 10:14 PM CDTTornado WatchSPCAshley, Chicot7 hr
Apr 19, 11:17 PM CDTMesoscale DiscussionSPCColumbia, Hempstead, Lafayette, Little River, Miller, Nevada and 1 more58 min
Apr 19, 11:45 PM CDTSevere Thunderstorm WatchSPCColumbia, Hempstead, Lafayette, Little River, Miller, Nevada and 1 more3 hr
Apr 20, 3:37 AM CDTSevere Thunderstorm WatchSPCAshley, Chicot8 hr
Apr 20, 12:46 PM CDTMesoscale DiscussionSPCAshley, Bradley, Calhoun, Chicot, Columbia, Desha and 8 more89 min
Apr 20, 1:02 PM CDTSevere Thunderstorm WatchSPCAshley, Chicot, Lee, Phillips7 hr
Apr 20, 2:04 PM CDTSevere Thunderstorm WatchSPCArkansas, Bradley, Calhoun, Clark, Cleburne, Cleveland and 36 more7 hr
Apr 20, 5:24 PM CDTMesoscale DiscussionSPCChicot, Drew96 min
Apr 20, 5:56 PM CDTMesoscale DiscussionSPCArkansas, Bradley, Calhoun, Clark, Cleveland, Dallas and 23 more2 hr
Apr 19, 9:03 PM CDTMesoscale DiscussionSPCBell, Coryell, Falls, Freestone, Henderson, Hill and 3 more57 min
Apr 20, 1:52 PM CDTMesoscale DiscussionSPCBell, Bosque, Brown, Burnet, Coleman, Comanche and 21 more53 min
Apr 20, 2:21 PM CDTSevere Thunderstorm WatchSPCBandera, Bell, Blanco, Burnet, Concho, Coryell and 20 more8 hr
Apr 20, 5:47 PM CDTMesoscale DiscussionSPCBlanco, Burnet, Concho, Crockett, Edwards, Gillespie and 15 more58 min

Nearby

Mesoscale Discussions in Arkansas, 2011Mesoscale Discussions in Texas, 2011Mesoscale Discussions in Oklahoma, 2011Every mesoscale discussion in 2011

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.