Alert archive / Louisiana / Mesoscale Discussions in 2020

Mesoscale Discussion 499

April 28, 2020Ashley County, Chicot County, Arkansas; 11 parishes in Louisiana; 11 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Apr 28, 2020, 11:57 PM CDT for Ashley County, Chicot County, Arkansas; 11 parishes in Louisiana; 11 counties in Mississippi. It was in force for 63 min.

The area

The outline as issued.

The facts

Issued: Apr 28, 2020, 11:57 PM CDT (04:57 UTC)
Expired: Apr 29, 2020, 1:00 AM CDT
In force: 63 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

All 24 counties

Ashley County, AR, Chicot County, AR, Caldwell Parish, LA, East Carroll Parish, LA, Franklin Parish, LA, Jackson Parish, LA, Madison Parish, LA, Morehouse Parish, LA, Ouachita Parish, LA, Richland Parish, LA, Tensas Parish, LA, Union Parish, LA, West Carroll Parish, LA, Bolivar County, MS, Carroll County, MS, Holmes County, MS, Humphreys County, MS, Issaquena County, MS, Leflore County, MS, Sharkey County, MS, Sunflower County, MS, Warren County, MS, Washington County, MS, Yazoo County, MS

The radar

The Jackson/Brandon,MS radar (KDGX), 146 km from the middle of the area, began a volume at 04:58 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 155Apr 29, 12:45 AM CDT

The nearest sounding before it

Shreveport, LA (KSHV), launched 00:00Z, 5.0 hours before the alert went out and 234 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: 733 J/kg
Mixed-layer CIN: -250 J/kg
Mixed-layer LCL: 1058 m above ground
0-6 km bulk shear: 43 kt
0-1 km storm-relative helicity: 119 m²/s²
0-3 km storm-relative helicity: 217 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

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
Apr 28, 7:35 PM CDT	Severe Thunderstorm Watch	SPC	Arkansas, Baxter, Boone, Bradley, Calhoun, Clark and 51 more	7 hr
Apr 28, 8:06 PM CDT	Mesoscale Discussion	SPC	Lafayette, Little River, Miller, Sevier	54 min
Apr 28, 8:25 PM CDT	Severe Thunderstorm Watch	SPC	Columbia, Hempstead, Howard, Lafayette, Little River, Miller and 3 more	9 hr
Apr 28, 10:08 PM CDT	Mesoscale Discussion	SPC	Clark, Cleburne, Conway, Craighead, Faulkner, Garland and 15 more	97 min
Apr 28, 11:12 PM CDT	Mesoscale Discussion	SPC	Arkansas, Bradley, Calhoun, Cleveland, Crittenden, Cross and 11 more	63 min
Apr 29, 12:48 AM CDT	Severe Thunderstorm Watch	SPC	Ashley, Chicot	4 hr
Apr 29, 1:56 AM CDT	Mesoscale Discussion	SPC	Allen, Avoyelles, Beauregard, Bienville, Caldwell, Catahoula and 19 more	2 hr
Apr 29, 2:40 AM CDT	Severe Thunderstorm Watch	SPC	Acadia, Allen, Ascension, Assumption, Avoyelles, Beauregard and 23 more	6 hr
Apr 29, 5:05 AM CDT	Mesoscale Discussion	SPC	Calcasieu, Cameron	115 min

Nearby

Mesoscale Discussions in Louisiana, 2020 Mesoscale Discussions in Mississippi, 2020 Mesoscale Discussions in Arkansas, 2020 Every mesoscale discussion in 2020

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.