Alert archive / Texas / Mesoscale Discussions in 2011
Mesoscale Discussion 484
The Storm Prediction Center issued this mesoscale discussion at Apr 19, 2011, 11:17 PM CDT for 7 counties in Arkansas; Bossier Parish, Caddo Parish, Webster Parish, Louisiana; 13 counties in Texas. It was in force for 58 min.
The area
The outline as issued.
The facts
- Issued
- Apr 19, 2011, 11:17 PM CDT (04:17 UTC)
- Expired
- Apr 20, 2011, 12:15 AM CDT
- In force
- 58 min
- Issued by
- the Storm Prediction Center
All 23 counties
Columbia County, AR, Hempstead County, AR, Lafayette County, AR, Little River County, AR, Miller County, AR, Nevada County, AR, Pike County, AR, Bossier Parish, LA, Caddo Parish, LA, Webster Parish, LA, Bowie County, TX, Camp County, TX, Cass County, TX, Franklin County, TX, Gregg County, TX, Harrison County, TX, Hopkins County, TX, Marion County, TX, Morris County, TX, Smith County, TX, Titus County, TX, Upshur County, TX, Wood County, TX
The radar
The Shreveport radar (KSHV), 76 km from the middle of the area, began a volume at 04:20 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, 4.3 hours before the alert went out and 76 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.
- 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
The text
As transmitted, in the capitals the NWS used until 2016.
244
ACUS11 KWNS 200417
SWOMCD
SPC MCD 200417
ARZ000-LAZ000-TXZ000-OKZ000-200515-
MESOSCALE DISCUSSION 0484
NWS STORM PREDICTION CENTER NORMAN OK
1117 PM CDT TUE APR 19 2011
AREAS AFFECTED...NERN TX...SWRN AR AND NWRN LA
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 200417Z - 200515Z
THUNDERSTORMS ARE EXPECTED TO CONTINUE DEVELOPING FROM NERN TX INTO
SWRN AR...EVENTUALLY SHIFTING SWD TOWARD NWRN LA. SUPERCELLS AND
LINE SEGMENTS WITH ISOLATED LARGE HAIL AND DAMAGING WIND WILL BE THE
MAIN THREATS...THOUGH AN ISOLATED TORNADO OR TWO CANNOT BE RULED
OUT.
GLANCING INFLUENCE OF SHORTWAVE TROUGH ADVANCING THROUGH ERN OK IS
APPARENTLY RESULTING IN SUFFICIENT FORCING FOR ASCENT TO REACTIVATE
BOUNDARY ACROSS NERN TX INTO SWRN AR. EFFECTIVE VERTICAL SHEAR OF
40-50 KT WILL CONTINUE TO SUPPORT SUPERCELLS...BUT SOME STORMS MAY
EVENTUALLY MERGE INTO LINE SEGMENTS AS WELL. ACTIVITY WILL SLOWLY
SHIFT SEWD WITH TIME WITH ISOLATED LARGE HAIL AND STRONG WIND GUSTS
THE MAIN THREATS. VWP AT SHREVEPORT STILL SHOWS A FAIRLY LARGE 0-1
KM HODOGRAPH...BUT TENDENCY SHOULD BE FOR THE LOW LEVEL SHEAR TO
GRADUALLY DECREASE AS THE LLJ VEERS AND SHIFTS EWD THROUGH THE TN
AND OH VALLEYS.
..DIAL.. 04/20/2011
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...LZK...SHV...FWD...
LAT...LON 32799306 32249406 32379561 33159577 33649481 34209364
33579286 32799306SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 19, 7:47 PM CDT | Mesoscale Discussion | SPC | Conway, Franklin, Howard, Johnson, Little River, Logan and 13 more | 88 min |
| Apr 19, 8:07 PM CDT | Mesoscale Discussion | SPC | Arkansas, Clay, Cleveland, Craighead, Crittenden, Cross and 18 more | 83 min |
| Apr 19, 10:14 PM CDT | Tornado Watch | SPC | Ashley, Chicot | 7 hr |
| Apr 19, 11:45 PM CDT | Severe Thunderstorm Watch | SPC | Columbia, Hempstead, Lafayette, Little River, Miller, Nevada and 1 more | 3 hr |
| Apr 20, 3:37 AM CDT | Severe Thunderstorm Watch | SPC | Ashley, Chicot | 8 hr |
| Apr 20, 12:46 PM CDT | Mesoscale Discussion | SPC | Ashley, Bradley, Calhoun, Chicot, Columbia, Desha and 8 more | 89 min |
| Apr 20, 1:02 PM CDT | Severe Thunderstorm Watch | SPC | Ashley, Chicot, Lee, Phillips | 7 hr |
| Apr 20, 2:04 PM CDT | Severe Thunderstorm Watch | SPC | Arkansas, Bradley, Calhoun, Clark, Cleburne, Cleveland and 36 more | 7 hr |
| Apr 20, 5:24 PM CDT | Mesoscale Discussion | SPC | Chicot, Drew | 96 min |
| Apr 20, 5:56 PM CDT | Mesoscale Discussion | SPC | Arkansas, Bradley, Calhoun, Clark, Cleveland, Dallas and 23 more | 2 hr |
| Apr 19, 9:03 PM CDT | Mesoscale Discussion | SPC | Bell, Coryell, Falls, Freestone, Henderson, Hill and 3 more | 57 min |
| Apr 20, 1:52 PM CDT | Mesoscale Discussion | SPC | Bell, Bosque, Brown, Burnet, Coleman, Comanche and 21 more | 53 min |
| Apr 20, 2:21 PM CDT | Severe Thunderstorm Watch | SPC | Bandera, Bell, Blanco, Burnet, Concho, Coryell and 20 more | 8 hr |
| Apr 20, 5:47 PM CDT | Mesoscale Discussion | SPC | Blanco, Burnet, Concho, Crockett, Edwards, Gillespie and 15 more | 58 min |
Nearby
Mesoscale Discussions in Texas, 2011Mesoscale Discussions in Arkansas, 2011Mesoscale Discussions in Louisiana, 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.