Alert archive / Mississippi / Mesoscale Discussions in 2012

Mesoscale Discussion 979

May 30, 20128 counties in Arkansas; 7 parishes in Louisiana; 27 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at May 30, 2012, 12:07 PM CDT for 8 counties in Arkansas; 7 parishes in Louisiana; 27 counties in Mississippi. It was in force for 83 min.

The area

The outline as issued.

The facts

Issued: May 30, 2012, 12:07 PM CDT (17:07 UTC)
Expired: May 30, 2012, 1:30 PM CDT
In force: 83 min
Issued by: the Storm Prediction Center
Chance of a watch: 60%

All 42 counties

Arkansas County, AR, Ashley County, AR, Chicot County, AR, Desha County, AR, Lee County, AR, Monroe County, AR, Phillips County, AR, Prairie County, AR, East Carroll Parish, LA, Franklin Parish, LA, Madison Parish, LA, Morehouse Parish, LA, Richland Parish, LA, Tensas Parish, LA, West Carroll Parish, LA, Attala County, MS, Bolivar County, MS, Carroll County, MS, Claiborne County, MS, Coahoma County, MS, Copiah County, MS, Grenada County, MS, Hinds County, MS, Holmes County, MS, Humphreys County, MS, Issaquena County, MS, Jefferson County, MS, Leflore County, MS, Madison County, MS, Montgomery County, MS, Panola County, MS, Quitman County, MS, Rankin County, MS, Sharkey County, MS, Sunflower County, MS, Tallahatchie County, MS, Tate County, MS, Tunica County, MS, Warren County, MS, Washington County, MS, Yalobusha County, MS, Yazoo County, MS

The radar

The Jackson/Brandon,MS radar (KDGX), 130 km from the middle of the area, began a volume at 17:07 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.

Severe Thunderstorm Watch 321May 30, 12:30 PM CDT

The nearest sounding before it

Jackson, MS (KJAN), launched 12:00Z, 5.1 hours before the alert went out and 121 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: 1192 J/kg
Mixed-layer CIN: -72 J/kg
Mixed-layer LCL: 1334 m above ground
0-6 km bulk shear: 16 kt
0-1 km storm-relative helicity: 14 m²/s²
0-3 km storm-relative helicity: -4 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

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

880 
ACUS11 KWNS 301707
SWOMCD
SPC MCD 301707 
MSZ000-ARZ000-LAZ000-301830-

MESOSCALE DISCUSSION 0979
NWS STORM PREDICTION CENTER NORMAN OK
1207 PM CDT WED MAY 30 2012

AREAS AFFECTED...SE AR...WRN MS...NE LA

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 301707Z - 301830Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...AN ISOLATED THREAT FOR HAIL AND WIND DAMAGE WILL LIKELY
DEVELOP ACROSS THE LOWER TO MID MS VALLEY THIS AFTERNOON. AS THE
STORMS INTENSIFY...WW ISSUANCE WILL BE POSSIBLE ACROSS THE REGION.

DISCUSSION...A SHORT LINE SEGMENT IS CURRENTLY ONGOING JUST TO THE
EAST OF LITTLE ROCK AR LOCATED ON THE LEADING EDGE OF STRONG
LARGE-SCALE ASCENT ASSOCIATED WITH A PRONOUNCED SHORTWAVE TROUGH
MOVING ACROSS THE MS RIVER IN FAR SRN IL. THE STORMS ARE ALSO
LOCATED ON THE FAR NRN EDGE OF MODERATE INSTABILITY WITH
MESOANALYSIS ESTIMATING MLCAPE IN THE 1000 TO 1500 J/KG RANGE ACROSS
NE LA...SE AR AND WCNTRL MS. THE INSTABILITY ALONG WITH ABOUT 30 KT
OF DEEP LAYER SHEAR EVIDENT ON REGIONAL WSR-88D VWPS SHOULD BE
SUFFICIENT FOR SEVERE MULTICELL LINE SEGMENTS. AS DESTABILIZATION
CONTINUES EARLY THIS AFTERNOON AND LOW-LEVEL LAPSE RATES STEEPEN...A
WIND DAMAGE THREAT SHOULD DEVELOP. IN ADDITION...A POCKET OF STEEP
MID-LEVEL LAPSE RATES IS ANALYZED OVER SE AR AND NW MS WITH 850 TO
500 MB LAPSE RATES OF 7.5 C/KM. THIS SHOULD RESULT IN AN ISOLATED
LARGE HAIL THREAT ESPECIALLY AS INSTABILITY CONTINUES TO INCREASE
OVER THE NEXT FEW HOURS.

..BROYLES/WEISS.. 05/30/2012

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

ATTN...WFO...MEG...JAN...LZK...SHV...

LAT...LON   34969169 33629169 31979214 31609149 31679054 32079000
            32738966 33848942 34758989 34969169

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 30, 12:27 PM CDT	Severe Thunderstorm Watch	SPC	Arkansas, Chicot, Desha, Lee, Monroe, Phillips	7 hr
May 30, 4:56 PM CDT	Mesoscale Discussion	SPC	Chicot, Desha, Lee, Phillips	94 min
May 30, 2:34 PM CDT	Mesoscale Discussion	SPC	Attala, Bolivar, Calhoun, Carroll, Chickasaw, Choctaw and 29 more	56 min

Nearby

Mesoscale Discussions in Mississippi, 2012 Mesoscale Discussions in Arkansas, 2012 Mesoscale Discussions in Louisiana, 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.