Alert archive / Louisiana / Mesoscale Discussions in 2020

Mesoscale Discussion 1869

December 23, 202035 parishes in Louisiana; 5 counties in Mississippi; 7 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Dec 23, 2020, 5:59 PM CST for 35 parishes in Louisiana; 5 counties in Mississippi; 7 counties in Texas. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Dec 23, 2020, 5:59 PM CST (23:59 UTC)
Expired: Dec 23, 2020, 8:30 PM CST
In force: 3 hr
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch possible
Chance of a watch: 40%

All 47 counties

Acadia Parish, LA, Allen Parish, LA, Avoyelles Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Caldwell Parish, LA, Cameron Parish, LA, Catahoula Parish, LA, Concordia Parish, LA, East Baton Rouge Parish, LA, East Carroll Parish, LA, East Feliciana Parish, LA, Evangeline Parish, LA, Franklin Parish, LA, Grant Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Davis Parish, LA, Lafayette Parish, LA, LaSalle Parish, LA, Madison Parish, LA, Natchitoches Parish, LA, Pointe Coupee Parish, LA, Rapides Parish, LA, Richland Parish, LA, Sabine Parish, LA, Saint Landry Parish, LA, Saint Martin Parish, LA, Tensas Parish, LA, Vermilion Parish, LA, Vernon Parish, LA, West Baton Rouge Parish, LA, West Carroll Parish, LA, West Feliciana Parish, LA, Winn Parish, LA, Adams County, MS, Claiborne County, MS, Franklin County, MS, Jefferson County, MS, Wilkinson County, MS, Hardin County, TX, Jasper County, TX, Jefferson County, TX, Newton County, TX, Orange County, TX, Sabine County, TX, Tyler County, TX

The radar

The Ft Polk radar (KPOE), 57 km from the middle of the area, began a volume at 00:05 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.

Tornado Watch 516Dec 23, 8:40 PM CST

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 12:00Z, 12.0 hours before the alert went out and 312 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 992 m above ground
0-6 km bulk shear: 33 kt
0-1 km storm-relative helicity: 176 m²/s²
0-3 km storm-relative helicity: 251 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
Dec 23, 3:27 PM CST	Mesoscale Discussion	SPC	Allen, Beauregard, Bienville, Bossier, Caddo, Calcasieu and 17 more	2 hr

Nearby

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