Alert archive / Arkansas / Mesoscale Discussions in 2012

Mesoscale Discussion 1529

July 21, 20124 states

The Storm Prediction Center issued this mesoscale discussion at Jul 21, 2012, 2:47 PM CDT for 4 states. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Jul 21, 2012, 2:47 PM CDT (19:47 UTC)
Expired: Jul 21, 2012, 5:15 PM CDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 5%

All 59 counties

Colbert County, AL, Franklin County, AL, Lauderdale County, AL, Lawrence County, AL, Limestone County, AL, Madison County, AL, Arkansas County, AR, Bradley County, AR, Calhoun County, AR, Clark County, AR, Cleveland County, AR, Columbia County, AR, Dallas County, AR, Desha County, AR, Drew County, AR, Grant County, AR, Hempstead County, AR, Hot Spring County, AR, Howard County, AR, Jefferson County, AR, Lee County, AR, Lincoln County, AR, Lonoke County, AR, Monroe County, AR, Nevada County, AR, Ouachita County, AR, Phillips County, AR, Pike County, AR, Prairie County, AR, St. Francis County, AR, Union County, AR, Alcorn County, MS, Benton County, MS, Bolivar County, MS, Coahoma County, MS, DeSoto County, MS, Itawamba County, MS, Lafayette County, MS, Lee County, MS, Marshall County, MS, Panola County, MS, Pontotoc County, MS, Prentiss County, MS, Quitman County, MS, Tallahatchie County, MS, Tate County, MS, Tippah County, MS, Tishomingo County, MS, Tunica County, MS, Union County, MS, Fayette County, TN, Franklin County, TN, Giles County, TN, Hardeman County, TN, Hardin County, TN, Lawrence County, TN, Lincoln County, TN, McNairy County, TN, Wayne County, TN

The radar

The Memphis radar (KNQA), 117 km from the middle of the area, began a volume at 19:49 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 12:00Z, 7.8 hours before the alert went out and 64 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: 947 J/kg
Mixed-layer CIN: -161 J/kg
Mixed-layer LCL: 1082 m above ground
0-6 km bulk shear: 3 kt
0-1 km storm-relative helicity: -27 m²/s²
0-3 km storm-relative helicity: 80 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 3.5

Open this sounding in Storm Lab

The text

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

161 
ACUS11 KWNS 211948
SWOMCD
SPC MCD 211947
ALZ000-TNZ000-MSZ000-ARZ000-212215-

MESOSCALE DISCUSSION 1529
NWS STORM PREDICTION CENTER NORMAN OK
0247 PM CDT SAT JUL 21 2012

AREAS AFFECTED...SRN AR...NRN MS...NRN AL...PARTS OF FAR SRN TN

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 211947Z - 212215Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...A VERY ISOLATED THREAT FOR SVR THUNDERSTORMS WILL EXIST
ACROSS PARTS OF THE MID-SOUTH THROUGH THE AFTERNOON...AND WW
ISSUANCE IS NOT NEEDED.

DISCUSSION...LATEST SFC MESOANALYSIS INDICATES A QUASI-STATIONARY
FRONT EXTENDING FROM NORTH OF DE QUEEN AR TOWARD SRN SECTIONS OF THE
MEMPHIS AREA AND FARTHER EAST INTO FAR SRN PARTS OF MIDDLE TN.
VISIBLE SATELLITE LOOP INDICATES INCREASINGLY AGITATED CUMULUS ALONG
THE BOUNDARY. THIS IS ESPECIALLY THE CASE WITHIN 50-75 MILES EITHER
SIDE OF THE MISSISSIPPI RIVER...WHERE WATER VAPOR IMAGERY REVEALS A
ZONE OF MODESTLY ENHANCED MID-LEVEL MOISTURE...PERHAPS IN
ASSOCIATION WITH A LOBE OF ASCENT ACCOMPANYING A SWD-MOVING IMPULSE
OVER THE ERN FLANK OF A CNTRL CONUS RIDGE. OTHERWISE...THE REGION IS
DISPLACED TO THE N/NW OF A PLUME OF RICHER DEEP MOISTURE...WITH
COMPARATIVELY MORE DRY AIR IN PLACE ACROSS THE AREA -- PW BETWEEN
1.5 AND 1.6 INCHES PER GPS DATA. HOWEVER...STEEP LOW-LEVEL LAPSE
RATES AMIDST SFC DEWPOINTS IN THE LOWER/MIDDLE 70S ARE SUPPORTING
GENERALLY 1500-2500 J/KG OF MLCAPE NEAR AND SOUTH OF THE
FRONT...WHICH WILL YIELD A THREAT FOR VIGOROUS CONVECTIVE UPDRAFTS
WITH SWWD/SWD-MOVING STORMS INTO EARLY EVENING.

ALONG WITH A VERY ISOLATED THREAT FOR MARGINALLY SVR HAIL...A DMGG
WIND GUST OR TWO CANNOT BE RULED OUT GIVEN DCAPE VALUES IN EXCESS OF
1100 J/KG. HOWEVER...EFFECTIVE BULK SHEAR MAGNITUDES AOB 20 KT
FOSTERING A PREDOMINANTLY PULSE CONVECTIVE MODE...AND THE
ANTICIPATED LIMITED STORM COVERAGE OWING TO RELATIVELY DRIER AIR
ALOFT IN PLACE...SHOULD KEEP ANY SVR THREAT VERY ISOLATED.

..COHEN/HART.. 07/21/2012

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

ATTN...WFO...OHX...BMX...HUN...MEG...JAN...LZK...SHV...

LAT...LON   35169009 35308892 35338739 35218609 34898587 34578646
            34278807 34048975 33809039 33209178 33099288 33289373
            33639409 34089424 34439366 34639249 34939132 35169009

Nearby

Mesoscale Discussions in Arkansas, 2012 Mesoscale Discussions in Mississippi, 2012 Mesoscale Discussions in Tennessee, 2012 Every mesoscale discussion in 2012

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.