Alert archive / Mississippi / Mesoscale Discussions in 2012

Mesoscale Discussion 742

May 7, 201220 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at May 7, 2012, 11:00 AM CDT for 20 counties in Mississippi. It was in force for 90 min.

The area

The outline as issued.

The facts

Issued: May 7, 2012, 11:00 AM CDT (16:00 UTC)
Expired: May 7, 2012, 12:30 PM CDT
In force: 90 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

Counties Attala County, MS, Choctaw County, MS, Clay County, MS, Hinds County, MS, Kemper County, MS, Lauderdale County, MS, Leake County, MS, Lowndes County, MS, Madison County, MS, Neshoba County, MS, Newton County, MS, Noxubee County, MS, Oktibbeha County, MS, Rankin County, MS, Scott County, MS, Simpson County, MS, Smith County, MS, Warren County, MS, Winston County, MS, Yazoo County, MS

The radar

The Jackson/Brandon,MS radar (KDGX), 74 km from the middle of the area, began a volume at 16:01 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 262May 7, 1:10 PM CDT

The nearest sounding before it

Jackson, MS (KJAN), launched 12:00Z, 4.0 hours before the alert went out and 75 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: 2057 J/kg
Mixed-layer CIN: -12 J/kg
Mixed-layer LCL: 496 m above ground
0-6 km bulk shear: 8 kt
0-1 km storm-relative helicity: -24 m²/s²
0-3 km storm-relative helicity: -21 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.

811 
ACUS11 KWNS 071601
SWOMCD
SPC MCD 071600
ALZ000-MSZ000-LAZ000-071730-

MESOSCALE DISCUSSION 0742
NWS STORM PREDICTION CENTER NORMAN OK
1100 AM CDT MON MAY 07 2012

AREAS AFFECTED...CNTRL MS...W CNTRL AL

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 071600Z - 071730Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...STORMS ARE EXPECTED TO CONTINUE TO DEVELOP AND SPREAD
SOUTHEASTWARD ACROSS THE REGION THROUGH EARLY AFTERNOON.  IT IS NOT
OUT OF THE QUESTION THAT ACTIVITY COULD STRENGTHEN ENOUGH TO REQUIRE
A SEVERE WEATHER WATCH...PARTICULARLY ACROSS WEST CENTRAL
MISSISSIPPI...WITHIN THE NEXT COUPLE OF HOURS.

DISCUSSION...LARGE-SCALE FORCING FOR UPWARD VERTICAL MOTION APPEARS
NEGLIGIBLE WITHIN A LIGHT FLOW...VERY WEAKLY SHEARED REGIME ACROSS
THE LOWER MISSISSIPPI VALLEY.  BUT LIFT ALONG A REMNANT OUTFLOW
ASSOCIATED WITH AN OVERNIGHT MESOSCALE CONVECTIVE SYSTEM IS
MAINTAINING FAIRLY VIGOROUS CONVECTIVE DEVELOPMENT AS IT ADVANCES
SOUTHEASTWARD THROUGH NORTHWESTERN/NORTHERN MISSISSIPPI AROUND 25
KT.  A MOIST BOUNDARY LAYER AHEAD OF THE LEADING EDGE OF THE OUTFLOW
IS BECOMING MODERATELY UNSTABLE...WITH INSOLATION CONTRIBUTING TO
MIXED LAYER CAPE OF 1000 TO 2000 J/KG...ALONG AN AXIS ACROSS CENTRAL
MISSISSIPPI INTO WEST CENTRAL ALABAMA.  THIS PROBABLY WILL SUPPORT
CONTINUING CONVECTIVE DEVELOPMENT...ALONG WITH A GRADUAL
INTENSIFICATION AND UPSCALE CONVECTIVE GROWTH THROUGH 18-19Z...WITH
STRONGEST STORMS LIKELY TO IMPACT AREAS NEAR AND WEST OF JACKSON.
MARGINALLY SEVERE HAIL APPEARS THE GENERAL PRIMARY SEVERE
THREAT...AT LEAST INITIALLY...BUT IT IS POSSIBLE THAT COLD POOL
STRENGTHENING COULD EVENTUALLY BECOME SUFFICIENT TO SUPPORT AN
INCREASING RISK FOR POTENTIALLY DAMAGING WIND GUSTS.

..KERR.. 05/07/2012

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

ATTN...WFO...BMX...JAN...

LAT...LON   32869076 33059016 33398963 33698916 33698877 33448819
            32978807 32548829 32138901 31839000 32089082 32519092
            32869076

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 7, 1:07 PM CDT	Severe Thunderstorm Watch	SPC	Adams, Amite, Claiborne, Clarke, Copiah, Covington and 30 more	5 hr
May 7, 3:53 PM CDT	Mesoscale Discussion	SPC	Adams, Amite, Claiborne, Clarke, Copiah, Covington and 21 more	97 min

Nearby

Mesoscale Discussions in Mississippi, 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.