Alert archive / Mississippi / Mesoscale Discussions in 2012

Mesoscale Discussion 985

May 30, 20124 counties in Arkansas; East Carroll Parish, Madison Parish, West Carroll Parish, Louisiana; 45 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at May 30, 2012, 4:56 PM CDT for 4 counties in Arkansas; East Carroll Parish, Madison Parish, West Carroll Parish, Louisiana; 45 counties in Mississippi. It was in force for 94 min.

The area

The outline as issued.

The facts

Issued: May 30, 2012, 4:56 PM CDT (21:56 UTC)
Expired: May 30, 2012, 6:30 PM CDT
In force: 94 min
Issued by: the Storm Prediction Center

All 52 counties

Chicot County, AR, Desha County, AR, Lee County, AR, Phillips County, AR, East Carroll Parish, LA, Madison Parish, LA, West Carroll Parish, LA, Alcorn County, MS, Attala County, MS, Benton County, MS, Bolivar County, MS, Calhoun County, MS, Carroll County, MS, Chickasaw County, MS, Choctaw County, MS, Clay County, MS, Coahoma County, MS, DeSoto County, MS, Grenada County, MS, Hinds County, MS, Holmes County, MS, Humphreys County, MS, Issaquena County, MS, Lafayette County, MS, Leake County, MS, Lee County, MS, Leflore County, MS, Madison County, MS, Marshall County, MS, Montgomery County, MS, Neshoba County, MS, Newton County, MS, Oktibbeha County, MS, Panola County, MS, Pontotoc County, MS, Prentiss County, MS, Quitman County, MS, Rankin County, MS, Scott County, MS, Sharkey County, MS, Sunflower County, MS, Tallahatchie County, MS, Tate County, MS, Tippah County, MS, Tunica County, MS, Union County, MS, Warren County, MS, Washington County, MS, Webster County, MS, Winston County, MS, Yalobusha County, MS, Yazoo County, MS

The radar

The Jackson/Brandon,MS radar (KDGX), 169 km from the middle of the area, began a volume at 21:56 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, 9.9 hours before the alert went out and 120 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: 312 J/kg
Mixed-layer CIN: -243 J/kg
Mixed-layer LCL: 1633 m above ground
0-6 km bulk shear: 27 kt
0-1 km storm-relative helicity: -4 m²/s²
0-3 km storm-relative helicity: 50 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 2.1

Open this sounding in Storm Lab

The text

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

281 
ACUS11 KWNS 302157
SWOMCD
SPC MCD 302156
MSZ000-ARZ000-LAZ000-302330-

MESOSCALE DISCUSSION 0985
NWS STORM PREDICTION CENTER NORMAN OK
0456 PM CDT WED MAY 30 2012

AREAS AFFECTED...PORTIONS OF CNTRL/SRN MS AND FAR NERN LA

CONCERNING...SEVERE THUNDERSTORM WATCH 321...

VALID 302156Z - 302330Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 321
CONTINUES.

SUMMARY...SEVERE WIND AND MARGINALLY SEVERE HAIL THREAT WILL
CONTINUE THE NEXT HOUR OR TWO. THE OVERALL TREND WILL BE FOR
CONVECTION TO WEAKEN WITH LOSS OF DAYTIME HEATING AND DOWNSTREAM
ENVIRONMENT BECOMING UNFAVORABLE FOR SUPPORTING STRONG/ORGANIZED
THUNDERSTORMS. A NEW WW IS NOT EXPECTED DOWNSTREAM.

DISCUSSION...THUNDERSTORM ACTIVITY HAS BECOME MORE DISORGANIZED OVER
THE LAST HOUR OR SO AND THIS TREND IS EXPECTED WITH S/SEWD
PROPAGATION DUE TO CONTINUED WEAKENING OF DEEP LAYER SHEAR.
ADDITIONALLY...THE THUNDERSTORMS HAVE CONTINUED TO MOVE AWAY FROM
AREA OF DEEP LAYER FORCING FOR ASCENT PROVIDED BY VORT MAX INDICATED
BY WATER VAPOR IMAGERY OVER WRN AR AS OF 2130Z.  WHILE STEEP
LOW-LEVEL LAPSE RATES AND LARGE T/TD SPREADS WILL CONTINUE TO POSE A
THREAT FOR STRONG/POTENTIALLY DAMAGING WIND GUSTS THE NEXT COUPLE OF
HOURS...THE OVERALL TREND IS FOR CONVECTION TO WEAKEN WITH THE LOSS
OF DAYTIME HEATING AND THE COINCIDENT DOWNSTREAM ENVIRONMENT
BECOMING LESS FAVORABLE FOR SUPPORTING STRONG/ORGANIZED
THUNDERSTORMS. THEREFORE...A WATCH EXTENSION OR NEW WATCH ISSUANCE
IS NOT ANTICIPATED DOWNSTREAM OF WW 321. HOWEVER...WFO JAN MAY NEED
TO ADD A FEW COUNTIES SHOULD STRONG/SEVERE STORMS MOVE OUT OF WW 321
BEFORE WATCH EXPIRATION TIME.

..LEITMAN.. 05/30/2012

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

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

LAT...LON   34929112 34928845 32068897 32099159 34929112

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 30, 12:07 PM CDT	Mesoscale Discussion	SPC	Arkansas, Ashley, Chicot, Desha, Lee, Monroe and 2 more	83 min
May 30, 12:27 PM CDT	Severe Thunderstorm Watch	SPC	Arkansas, Chicot, Desha, Lee, Monroe, Phillips	7 hr
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.