Alert archive / Mississippi / Mesoscale Discussions in 2017

Mesoscale Discussion 98

January 21, 20177 parishes in Louisiana; 9 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Jan 21, 2017, 8:14 PM CST for 7 parishes in Louisiana; 9 counties in Mississippi. It was in force for 61 min.

The area

The outline as issued.

The facts

Issued: Jan 21, 2017, 8:14 PM CST (02:14 UTC)
Expired: Jan 21, 2017, 9:15 PM CST
In force: 61 min
Issued by: the Storm Prediction Center

Counties East Feliciana Parish, LA, Livingston Parish, LA, Saint Helena Parish, LA, Saint Tammany Parish, LA, Tangipahoa Parish, LA, Washington Parish, LA, West Feliciana Parish, LA, Amite County, MS, George County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Pearl River County, MS, Pike County, MS, Stone County, MS, Wilkinson County, MS

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 00:00Z, 2.2 hours before the alert went out and 80 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: 1796 J/kg
Mixed-layer CIN: -13 J/kg
Mixed-layer LCL: 528 m above ground
0-6 km bulk shear: 96 kt
0-1 km storm-relative helicity: 288 m²/s²
0-3 km storm-relative helicity: 382 m²/s²
Significant tornado parameter: 4.0
Supercell composite: 16.4

Open this sounding in Storm Lab

The text

As transmitted.

759 
ACUS11 KWNS 220214
SWOMCD
SPC MCD 220214 
MSZ000-LAZ000-220315-

Mesoscale Discussion 0098
NWS Storm Prediction Center Norman OK
0814 PM CST Sat Jan 21 2017

Areas affected...Parts of southeast Louisiana into adjacent southern
Mississippi

Concerning...Tornado Watch 15...

Valid 220214Z - 220315Z

The severe weather threat for Tornado Watch 15 continues.

SUMMARY...Severe/tornado risk continues to gradually shift northeast
out of Tornado Watch 15 into adjacent watches.

DISCUSSION...Latest radar loop shows isolated strong/locally severe
storms moving east-northeast across parts of southeast Louisiana
mainly north of I-10/I-12, near and north of the slowly
northward-advancing warm front.  The evening LIX RAOB revealed a
very potent severe-storm environment -- both kinematically and
thermodynamically -- in the vicinity of the front, which continues
to spread northeast into parts of Mississippi and Alabama.  Though
local risk may linger across WW 15 beyond the scheduled 22/03Z
expiration, expect the main severe/tornado potential to shift north
of the watch over the next couple of hours.

..Goss.. 01/22/2017

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...MOB...JAN...LIX...

LAT...LON   30968944 30908844 30458844 30249031 30799155 31169158
            31329120 31249039 30968944

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jan 21, 6:05 PM CST	Mesoscale Discussion	SPC	Ascension, Assumption, Avoyelles, Catahoula, Concordia, East Baton Rouge and 22 more	85 min
Jan 21, 7:50 PM CST	Tornado Watch	SPC	Catahoula, Concordia, East Carroll, Franklin, Madison, Morehouse and 3 more	4 hr
Jan 21, 8:22 PM CST	Mesoscale Discussion	SPC	Bienville, Caldwell, Catahoula, Claiborne, Concordia, East Carroll and 13 more	113 min
Jan 21, 6:51 PM CST	Tornado Watch PDS	SPC	George, Greene, Perry, Stone, Wayne	8 hr
Jan 21, 8:30 PM CST	Mesoscale Discussion	SPC	Wayne	90 min
Jan 21, 9:57 PM CST	Mesoscale Discussion	SPC	Wayne	93 min

Nearby

Mesoscale Discussions in Mississippi, 2017 Mesoscale Discussions in Louisiana, 2017 Every mesoscale discussion in 2017

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.