Alert archive / Louisiana / Mesoscale Discussions in 2018

Mesoscale Discussion 1737

December 27, 201825 parishes in Louisiana; 22 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Dec 27, 2018, 1:50 PM CST for 25 parishes in Louisiana; 22 counties in Mississippi. It was in force for 85 min.

The area

The outline as issued.

The facts

Issued: Dec 27, 2018, 1:50 PM CST (19:50 UTC)
Expired: Dec 27, 2018, 3:15 PM CST
In force: 85 min
Issued by: the Storm Prediction Center

All 47 counties

Ascension Parish, LA, Assumption Parish, LA, Catahoula Parish, LA, Concordia Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Franklin Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Livingston Parish, LA, Madison Parish, LA, Orleans Parish, LA, Pointe Coupee Parish, LA, Saint Charles Parish, LA, Saint Helena Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Martin Parish, LA, Saint Tammany Parish, LA, St. Mary Parish, LA, Tangipahoa Parish, LA, Tensas Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Adams County, MS, Amite County, MS, Claiborne County, MS, Copiah County, MS, Covington County, MS, Franklin County, MS, Hinds County, MS, Jefferson County, MS, Jefferson Davis County, MS, Lawrence County, MS, Leake County, MS, Lincoln County, MS, Madison County, MS, Marion County, MS, Pearl River County, MS, Pike County, MS, Rankin County, MS, Scott County, MS, Simpson County, MS, Walthall County, MS, Warren County, MS, Wilkinson County, MS

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 12:00Z, 7.8 hours before the alert went out and 138 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: 53 J/kg
Mixed-layer CIN: -292 J/kg
Mixed-layer LCL: 564 m above ground
0-6 km bulk shear: 54 kt
0-1 km storm-relative helicity: 651 m²/s²
0-3 km storm-relative helicity: 836 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 26, 11:40 PM CST	Mesoscale Discussion	SPC	Bossier, Caddo, De Soto	2 hr
Dec 27, 12:02 AM CST	Severe Thunderstorm Watch	SPC	Bienville, Bossier, Caddo, Claiborne, De Soto, Red River and 1 more	5 hr
Dec 27, 1:39 AM CST	Mesoscale Discussion	SPC	Bienville, Bossier, Caddo, Claiborne, De Soto, Lincoln and 2 more	2 hr
Dec 27, 3:09 AM CST	Mesoscale Discussion	SPC	Allen, Beauregard, Calcasieu, Cameron, Jefferson Davis, Vernon	2 hr
Dec 27, 3:43 AM CST	Tornado Watch	SPC	Acadia, Allen, Beauregard, Calcasieu, Caldwell, Cameron and 10 more	10 hr
Dec 27, 7:12 AM CST	Mesoscale Discussion	SPC	Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 11 more	2 hr
Dec 27, 9:00 AM CST	Mesoscale Discussion	SPC	Avoyelles, Catahoula, Concordia, East Baton Rouge, East Feliciana, Iberville and 6 more	60 min
Dec 27, 9:29 AM CST	Tornado Watch	SPC	Ascension, Assumption, Avoyelles, Catahoula, Concordia, East Baton Rouge and 27 more	9 hr

Nearby

Mesoscale Discussions in Louisiana, 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.