Alert archive / Mississippi / Mesoscale Discussions in 2018

Mesoscale Discussion 1331

August 20, 20184 states

The Storm Prediction Center issued this mesoscale discussion at Aug 20, 2018, 5:57 PM CDT for 4 states. It was in force for 63 min.

The area

The outline as issued.

The facts

Issued: Aug 20, 2018, 5:57 PM CDT (22:57 UTC)
Expired: Aug 20, 2018, 7:00 PM CDT
In force: 63 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

All 49 counties

Ashley County, AR, Chicot County, AR, East Carroll Parish, LA, Morehouse Parish, LA, Union 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, Holmes County, MS, Humphreys County, MS, Issaquena County, MS, Itawamba County, MS, Lafayette County, MS, Lee County, MS, Leflore County, MS, Marshall County, MS, Monroe County, MS, Montgomery County, MS, Oktibbeha County, MS, Panola County, MS, Pontotoc County, MS, Prentiss County, MS, Quitman County, MS, Sharkey County, MS, Sunflower County, MS, Tallahatchie County, MS, Tate County, MS, Tippah County, MS, Tishomingo County, MS, Tunica County, MS, Union County, MS, Washington County, MS, Webster County, MS, Yalobusha County, MS, Yazoo County, MS, Fayette County, TN, Hardeman County, TN, McNairy County, TN, Shelby County, TN

The radar

The Columbus AFB radar (KGWX), 156 km from the middle of the area, began a volume at 22:57 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 (KBYH), launched 12:00Z, 11.0 hours before the alert went out and 126 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: 904 J/kg
Mixed-layer CIN: -46 J/kg
Mixed-layer LCL: 737 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 81 m²/s²
0-3 km storm-relative helicity: 133 m²/s²
Significant tornado parameter: 0.5
Supercell composite: 3.7

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 20, 11:46 AM CDT	Mesoscale Discussion	SPC	Arkansas, Clay, Craighead, Crittenden, Cross, Greene and 16 more	119 min
Aug 20, 12:46 PM CDT	Severe Thunderstorm Watch	SPC	Baxter, Clay, Cleburne, Craighead, Crittenden, Cross and 21 more	7 hr
Aug 20, 3:14 PM CDT	Mesoscale Discussion	SPC	Ashley, Chicot	3 hr
Aug 20, 4:00 PM CDT	Mesoscale Discussion	SPC	Clay, Cleburne, Craighead, Crittenden, Cross, Greene and 16 more	2 hr
Aug 20, 4:45 PM CDT	Severe Thunderstorm Watch	SPC	Alcorn, Benton, Calhoun, Chickasaw, DeSoto, Itawamba and 14 more	6 hr

Nearby

Mesoscale Discussions in Mississippi, 2018 Mesoscale Discussions in Louisiana, 2018 Mesoscale Discussions in Tennessee, 2018 Every mesoscale discussion in 2018

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.