Alert archive / Arkansas / Mesoscale Discussions in 2011

Mesoscale Discussion 673

April 30, 201118 counties in Arkansas

The Storm Prediction Center issued this mesoscale discussion at Apr 30, 2011, 8:47 PM CDT for 18 counties in Arkansas. It was in force for 58 min.

The area

The outline as issued.

The facts

Issued
Apr 30, 2011, 8:47 PM CDT (01:47 UTC)
Expired
Apr 30, 2011, 9:45 PM CDT
In force
58 min
Issued by
the Storm Prediction Center

Counties Arkansas County, AR, Clark County, AR, Conway County, AR, Faulkner County, AR, Garland County, AR, Grant County, AR, Hot Spring County, AR, Jefferson County, AR, Lonoke County, AR, Montgomery County, AR, Perry County, AR, Pike County, AR, Polk County, AR, Prairie County, AR, Pulaski County, AR, Saline County, AR, White County, AR, Yell County, AR

The radar

The Little Rock radar (KLZK), 45 km from the middle of the area, began a volume at 01:49 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

Little Rock, AR (KLZK), launched 00:00Z, 1.8 hours before the alert went out and 255 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, Little Rock, AR at 00:00Z on 2011-05-01Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1745 joules per kilogram.LCLEL10008507005003002001001 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, Little Rock, AR at 00:00Z on 2011-05-01The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 281 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
1745 J/kg
Mixed-layer CIN
0 J/kg
Mixed-layer LCL
528 m above ground
0-6 km bulk shear
52 kt
0-1 km storm-relative helicity
281 m²/s²
0-3 km storm-relative helicity
322 m²/s²
Significant tornado parameter
3.2
Supercell composite
14.0

Open this sounding in Storm Lab

The text

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

660 
ACUS11 KWNS 010147
SWOMCD
SPC MCD 010147 
ARZ000-010245-

MESOSCALE DISCUSSION 0673
NWS STORM PREDICTION CENTER NORMAN OK
0847 PM CDT SAT APR 30 2011

AREAS AFFECTED...CENTRAL AR

CONCERNING...TORNADO WATCH 258...

VALID 010147Z - 010245Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 258 CONTINUES.

RECENT TRENDS PER LIT WSR-88D INDICATED THE STORM OVER GARLAND
COUNTY AR WAS BECOMING SUPERCELLULAR /INFLOW NOTCH AND LOW LEVEL
ROTATION/ AND TRACKING ESE AT 25 KT.  00Z LIT SOUNDING SHOWED THE
CAP HAD WEAKENED SINCE 12Z WITH A RATHER MOIST BOUNDARY LAYER AS
CURRENT SURFACE OBSERVATIONS ACROSS CENTRAL/SRN AR INDICATED AN
INCREASE IN SURFACE DEWPOINTS TO THE UPPER 60S.  THIS IS
CONTRIBUTING TO A MODERATELY UNSTABLE AIR MASS.  MEANWHILE...
STRENGTHENING SWLY LLJ TO 40 KT PER LIT WSR-88D VWP DATA IS
RESULTING IN INCREASING LOW LEVEL SHEAR /SFC-1 KM SRH 420 M2 PER
S2/.  THIS COMBINED WITH AFOREMENTIONED THERMODYNAMICS AND OBJECTIVE
ANALYSES SHOWING EFFECTIVE INFLOW IS SURFACE BASED PROVIDES CONCERN
THAT THIS STORM COULD PRODUCE A TORNADO.

OTHER STORMS DEVELOPING AND/OR MOVING INTO CENTRAL AR WILL NEED TO
BE MONITORED FOR SIMILAR TRENDS AND THREAT.

..PETERS.. 05/01/2011

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

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

LAT...LON   35259278 35459201 35309130 34219132 34109201 33889315
            34219440 34649438 35109327 35259278

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 30, 7:49 PM CDTMesoscale DiscussionSPCClay, Greene, Izard, Lawrence, Randolph, Sharp and 1 more56 min
Apr 30, 9:26 PM CDTMesoscale DiscussionSPCHempstead, Howard, Little River, Miller, Sevier64 min
Apr 30, 11:39 PM CDTMesoscale DiscussionSPCArkansas, Clark, Cleburne, Conway, Craighead, Cross and 31 more66 min
May 1, 1:16 AM CDTMesoscale DiscussionSPCArkansas, Clark, Cleburne, Conway, Craighead, Crittenden and 37 more59 min
May 1, 3:50 AM CDTMesoscale DiscussionSPCLee, Monroe, Phillips2 hr
May 1, 8:30 AM CDTMesoscale DiscussionSPCClark, Dallas, Garland, Hempstead, Hot Spring, Howard and 9 more30 min
May 1, 8:45 AM CDTSevere Thunderstorm WatchSPCClark, Columbia, Dallas, Garland, Hempstead, Hot Spring and 10 more6 hr
May 1, 12:12 PM CDTMesoscale DiscussionSPCArkansas, Ashley, Bradley, Calhoun, Clark, Cleveland and 34 more93 min
May 1, 12:47 PM CDTTornado WatchSPCArkansas, Bradley, Calhoun, Clark, Cleveland, Columbia and 27 more8 hr
May 1, 3:18 PM CDTMesoscale DiscussionSPCArkansas, Ashley, Bradley, Calhoun, Clark, Cleveland and 37 more87 min
May 1, 5:42 PM CDTMesoscale DiscussionSPCClark, Dallas, Garland, Grant, Hempstead, Hot Spring and 14 more3 hr
May 1, 5:43 PM CDTMesoscale DiscussionSPCArkansas, Ashley, Bradley, Calhoun, Clark, Cleveland and 37 more92 min

Nearby

Mesoscale Discussions in Arkansas, 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.