Alert archive / Louisiana / Mesoscale Discussions in 2020

Mesoscale Discussion 482

April 28, 202017 parishes in Louisiana; 8 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Apr 28, 2020, 10:09 AM CDT for 17 parishes in Louisiana; 8 counties in Texas. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Apr 28, 2020, 10:09 AM CDT (15:09 UTC)
Expired: Apr 28, 2020, 12:45 PM CDT
In force: 3 hr
Issued by: the Storm Prediction Center
Chance of a watch: 20%

All 25 counties

Allen Parish, LA, Avoyelles Parish, LA, Beauregard Parish, LA, Bienville Parish, LA, Caldwell Parish, LA, Catahoula Parish, LA, De Soto Parish, LA, Evangeline Parish, LA, Grant Parish, LA, Jackson Parish, LA, LaSalle Parish, LA, Natchitoches Parish, LA, Rapides Parish, LA, Red River Parish, LA, Sabine Parish, LA, Vernon Parish, LA, Winn Parish, LA, Angelina County, TX, Jasper County, TX, Nacogdoches County, TX, Newton County, TX, Sabine County, TX, San Augustine County, TX, Shelby County, TX, Tyler County, TX

The radar

The Ft Polk radar (KPOE), 59 km from the middle of the area, began a volume at 15:13 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

Lake Charles Mun, LA (KLCH), launched 12:00Z, 3.2 hours before the alert went out and 162 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: 1084 J/kg
Mixed-layer CIN: -71 J/kg
Mixed-layer LCL: 555 m above ground
0-6 km bulk shear: 20 kt
0-1 km storm-relative helicity: 181 m²/s²
0-3 km storm-relative helicity: 253 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 2.7

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
Apr 28, 12:47 PM CDT	Mesoscale Discussion	SPC	Allen, Beauregard, Calcasieu, Cameron, Jefferson Davis	118 min
Apr 28, 5:38 PM CDT	Mesoscale Discussion	SPC	Orleans, Saint Charles, Saint James, Saint John the Baptist, Saint Tammany, Washington	2 hr
Apr 28, 3:30 PM CDT	Severe Thunderstorm Watch	SPC	Archer, Clay, Wichita	8 hr

Nearby

Mesoscale Discussions in Louisiana, 2020 Mesoscale Discussions in Texas, 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.