Alert archive / Arkansas / Mesoscale Discussions in 2011

Mesoscale Discussion 832

May 20, 201114 counties in Arkansas; 4 parishes in Louisiana; 13 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at May 20, 2011, 9:06 PM CDT for 14 counties in Arkansas; 4 parishes in Louisiana; 13 counties in Texas. It was in force for 114 min.

The area

The outline as issued.

The facts

Issued: May 20, 2011, 9:06 PM CDT (02:06 UTC)
Expired: May 20, 2011, 11:00 PM CDT
In force: 114 min
Issued by: the Storm Prediction Center

All 31 counties

Clark County, AR, Columbia County, AR, Dallas County, AR, Garland County, AR, Grant County, AR, Hempstead County, AR, Hot Spring County, AR, Howard County, AR, Lafayette County, AR, Little River County, AR, Miller County, AR, Nevada County, AR, Ouachita County, AR, Pike County, AR, Bossier Parish, LA, Caddo Parish, LA, De Soto Parish, LA, Webster Parish, LA, Bowie County, TX, Camp County, TX, Cass County, TX, Cherokee County, TX, Gregg County, TX, Harrison County, TX, Marion County, TX, Morris County, TX, Panola County, TX, Rusk County, TX, Smith County, TX, Titus County, TX, Upshur County, TX

The radar

The Shreveport radar (KSHV), 54 km from the middle of the area, began a volume at 02:08 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 (KSHV), launched 00:00Z, 2.1 hours before the alert went out and 59 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: 1940 J/kg
Mixed-layer CIN: -23 J/kg
Mixed-layer LCL: 1407 m above ground
0-6 km bulk shear: 19 kt
0-1 km storm-relative helicity: 116 m²/s²
0-3 km storm-relative helicity: 248 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 9.0

Open this sounding in Storm Lab

The text

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

122 
ACUS11 KWNS 210207
SWOMCD
SPC MCD 210206
ARZ000-LAZ000-TXZ000-OKZ000-210400-

MESOSCALE DISCUSSION 0832
NWS STORM PREDICTION CENTER NORMAN OK
0906 PM CDT FRI MAY 20 2011

AREAS AFFECTED...NERN TX/SWRN AR/NWRN LA

CONCERNING...TORNADO WATCH 315...

VALID 210206Z - 210400Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 315 CONTINUES.

SEVERE THREAT CONTINUES TO DIMINISH SLOWLY WITH TIME.

LATEST RADAR LOOP SHOWS AN EXPANSIVE AREA OF THUNDERSTORMS EXTENDING
FROM SRN MO SSWWD INTO THE HILL COUNTRY OF TX.  MODERATELY UNSTABLE
AIRMASS PREVAILS AHEAD OF THE ONGOING CONVECTION FROM SRN AR
SWWD...WHERE LOW TO MID 70S DEWPOINTS ARE INDICATED.

STORMS ARE EVOLVING WITH TIME TOWARD A PRIMARILY LINEAR BAND...AND
AS SUCH TORNADO THREAT HAS DECREASED.  SOME POTENTIAL FOR DAMAGING
WINDS REMAINS...BUT EXPECT THE MAIN THREAT FROM HERE FORWARD TO BE
IN THE FORM OF HAIL.  ALONG WITH SEVERE POTENTIAL...HEAVY RAINFALL
IS ALSO POSSIBLE -- PARTICULARLY ACROSS PORTIONS OF NERN TX WHERE
STORMS ARE MOVING FAIRLY SLOWLY AND MANY AREAS EXPERIENCE
REPEATED/PROLONGED STORMS.

..GOSS.. 05/21/2011

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

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

LAT...LON   31709491 31899578 33109521 34619343 34589214 31929344
            31709491

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 21, 3:38 PM CDT	Mesoscale Discussion	SPC	Ashley, Columbia, Union	97 min
May 21, 1:18 PM CDT	Mesoscale Discussion	SPC	Bandera, Bosque, Burnet, Coryell, Erath, Gillespie and 12 more	117 min
May 21, 1:45 PM CDT	Severe Thunderstorm Watch	SPC	Bandera, Bell, Blanco, Bosque, Burnet, Comal and 29 more	7 hr
May 21, 3:53 PM CDT	Mesoscale Discussion	SPC	Bosque, Burnet, Coryell, Dallas, Ellis, Gillespie and 9 more	67 min
May 21, 5:42 PM CDT	Mesoscale Discussion	SPC	Bell, Blanco, Bosque, Burnet, Collin, Cooke and 28 more	2 hr

Nearby

Mesoscale Discussions in Arkansas, 2011 Mesoscale Discussions in Texas, 2011 Mesoscale Discussions in Louisiana, 2011 Every 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.