Alert archive / Tennessee / Mesoscale Discussions in 2018

Mesoscale Discussion 473

May 20, 20186 states

The Storm Prediction Center issued this mesoscale discussion at May 20, 2018, 11:43 AM CDT for 6 states. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: May 20, 2018, 11:43 AM CDT (16:43 UTC)
Expired: May 20, 2018, 2:15 PM CDT
In force: 3 hr
Issued by: the Storm Prediction Center
Chance of a watch: 60%

All 69 counties

Clay County, AR, Craighead County, AR, Crittenden County, AR, Cross County, AR, Greene County, AR, Independence County, AR, Jackson County, AR, Lawrence County, AR, Lee County, AR, Mississippi County, AR, Monroe County, AR, Phillips County, AR, Poinsett County, AR, Prairie County, AR, St. Francis County, AR, White County, AR, Woodruff County, AR, Alexander County, IL, Johnson County, IL, Massac County, IL, Pope County, IL, Pulaski County, IL, Union County, IL, Ballard County, KY, Calloway County, KY, Carlisle County, KY, Fulton County, KY, Graves County, KY, Hickman County, KY, Livingston County, KY, Marshall County, KY, McCracken County, KY, Bollinger County, MO, Butler County, MO, Cape Girardeau County, MO, Dunklin County, MO, Mississippi County, MO, New Madrid County, MO, Pemiscot County, MO, Scott County, MO, Stoddard County, MO, Benton County, MS, Coahoma County, MS, DeSoto County, MS, Lafayette County, MS, Marshall County, MS, Panola County, MS, Quitman County, MS, Tate County, MS, Tippah County, MS, Tunica County, MS, Carroll County, TN, Chester County, TN, Crockett County, TN, Dyer County, TN, Fayette County, TN, Gibson County, TN, Hardeman County, TN, Haywood County, TN, Henderson County, TN, Henry County, TN, Lake County, TN, Lauderdale County, TN, Madison County, TN, McNairy County, TN, Obion County, TN, Shelby County, TN, Tipton County, TN, Weakley County, TN

The radar

The Memphis radar (KNQA), 53 km from the middle of the area, began a volume at 16:48 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 110May 20, 12:30 PM CDT

The nearest sounding before it

Little Rock, AR (KBYH), launched 12:00Z, 4.7 hours before the alert went out and 105 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: 1368 J/kg
Mixed-layer CIN: -61 J/kg
Mixed-layer LCL: 1256 m above ground
0-6 km bulk shear: 8 kt
0-1 km storm-relative helicity: -28 m²/s²
0-3 km storm-relative helicity: -10 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

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
May 20, 1:11 AM CDT	Mesoscale Discussion	SPC	Polk, Scott, Sebastian	2 hr
May 20, 12:32 PM CDT	Severe Thunderstorm Watch	SPC	Clay, Craighead, Crittenden, Cross, Greene, Lawrence and 6 more	6 hr
May 20, 3:32 PM CDT	Mesoscale Discussion	SPC	Clay, Craighead, Crittenden, Cross, Greene, Lee and 4 more	118 min
May 20, 3:32 PM CDT	Severe Thunderstorm Watch	SPC	Benton	4 hr
May 20, 6:25 PM CDT	Mesoscale Discussion	SPC	Benton, Carroll	95 min
May 20, 6:26 PM CDT	Mesoscale Discussion	SPC	Arkansas, Craighead, Crittenden, Cross, Greene, Jackson and 8 more	64 min
May 20, 5:40 PM CDT	Mesoscale Discussion	SPC	Boone, Boyd, Bracken, Campbell, Carter, Fleming and 11 more	3 hr
May 19, 7:41 PM CDT	Mesoscale Discussion	SPC	Bates, Benton, Cass, Henry, Johnson, Pettis	94 min
May 20, 12:42 AM CDT	Mesoscale Discussion	SPC	Barton, Bates, Benton, Camden, Cass, Cedar and 28 more	3 hr
May 20, 2:24 PM CDT	Mesoscale Discussion	SPC	Barry, Barton, Bates, Benton, Camden, Cedar and 16 more	3 hr

Nearby

Mesoscale Discussions in Tennessee, 2018 Mesoscale Discussions in Arkansas, 2018 Mesoscale Discussions in Mississippi, 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.