Alert archive / Louisiana / Mesoscale Discussions in 2017

Mesoscale Discussion 375

March 29, 2017Ashley County, Chicot County, Drew County, Arkansas; 29 parishes in Louisiana; 16 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Mar 29, 2017, 9:58 PM CDT for Ashley County, Chicot County, Drew County, Arkansas; 29 parishes in Louisiana; 16 counties in Mississippi. It was in force for 92 min.

The area

The outline as issued.

The facts

Issued: Mar 29, 2017, 9:58 PM CDT (02:58 UTC)
Expired: Mar 29, 2017, 11:30 PM CDT
In force: 92 min
Issued by: the Storm Prediction Center

All 48 counties

Ashley County, AR, Chicot County, AR, Drew County, AR, Acadia Parish, LA, Allen Parish, LA, Avoyelles Parish, LA, Calcasieu Parish, LA, Caldwell Parish, LA, Cameron Parish, LA, Catahoula Parish, LA, Concordia Parish, LA, East Carroll Parish, LA, Evangeline Parish, LA, Franklin Parish, LA, Grant Parish, LA, Iberia Parish, LA, Jefferson Davis Parish, LA, Lafayette Parish, LA, LaSalle Parish, LA, Madison Parish, LA, Morehouse Parish, LA, Ouachita Parish, LA, Pointe Coupee Parish, LA, Rapides Parish, LA, Richland Parish, LA, Saint Landry Parish, LA, Saint Martin Parish, LA, Tensas Parish, LA, Vermilion Parish, LA, West Baton Rouge Parish, LA, West Carroll Parish, LA, West Feliciana Parish, LA, Adams County, MS, Carroll County, MS, Claiborne County, MS, Franklin County, MS, Hinds County, MS, Holmes County, MS, Humphreys County, MS, Issaquena County, MS, Jefferson County, MS, Leflore County, MS, Sharkey County, MS, Sunflower County, MS, Warren County, MS, Washington County, MS, Wilkinson County, MS, Yazoo County, MS

The radar

The Ft Polk radar (KPOE), 120 km from the middle of the area, began a volume at 03:02 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 00:00Z, 3.0 hours before the alert went out and 187 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: 1539 J/kg
Mixed-layer CIN: -1 J/kg
Mixed-layer LCL: 662 m above ground
0-6 km bulk shear: 56 kt
0-1 km storm-relative helicity: 157 m²/s²
0-3 km storm-relative helicity: 162 m²/s²
Significant tornado parameter: 1.1
Supercell composite: 4.5

Open this sounding in Storm Lab

The text

As transmitted.

991 
ACUS11 KWNS 300258
SWOMCD
SPC MCD 300258 
MSZ000-LAZ000-ARZ000-300430-

Mesoscale Discussion 0375
NWS Storm Prediction Center Norman OK
0958 PM CDT Wed Mar 29 2017

Areas affected...Portions of western MS...LA...southeast AR

Concerning...Tornado Watch 101...

Valid 300258Z - 300430Z

The severe weather threat for Tornado Watch 101 continues.

SUMMARY...The severe risk continues across Tornado Watch 101.

DISCUSSION...Clusters of deeper convection persist along the eastern
and southern fringes of a loosely organized MCS from the ArkLaMiss
to southern LA, with the most robust convection confined to southern
LA. Observational trends suggest low-level moistening east of this
activity, with surface dewpoints into the middle 60s extending
northward to the Interstate 20 corridor. This suggests that more
buoyant inflow may continue extending northward, allowing southern
LA convection and the associated severe risk to slowly develop
northeastward with time. The VAD wind profile at Jackson MS suggests
a veer-back structure with moderate deep and low-level shear, which
will continue to favor semi-organized cluster-type convective modes.
Damaging wind gusts and perhaps a couple of tornadoes may occur with
this activity, and eastward extensions of the watch may become
necessary later this evening. Otherwise, a separate cluster of
storms between Greenville and Vicksburg is advancing into lower
theta-e air in north-central MS and may subsequently weaken through
the evening. The severe risk is greatly lessening to the west of the
ongoing convection.

..Cohen.. 03/30/2017

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

ATTN...WFO...MEG...JAN...LIX...LZK...LCH...SHV...

LAT...LON   29549175 29559374 33719171 33728962 29549175

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Mar 29, 7:26 PM CDT	Tornado Watch	SPC	Ashley, Chicot	8 hr
Mar 29, 7:34 PM CDT	Mesoscale Discussion	SPC	Baxter, Boone, Clark, Conway, Fulton, Garland and 23 more	86 min
Mar 29, 9:44 PM CDT	Mesoscale Discussion	SPC	Baxter, Cleburne, Faulkner, Fulton, Independence, Izard and 6 more	91 min
Mar 30, 1:34 AM CDT	Mesoscale Discussion	SPC	Ascension, Assumption, East Baton Rouge, East Feliciana, Iberia, Iberville and 10 more	86 min
Mar 30, 11:10 AM CDT	Mesoscale Discussion	SPC	Harrison, Jackson	65 min

Nearby

Mesoscale Discussions in Louisiana, 2017 Mesoscale Discussions in Mississippi, 2017 Mesoscale Discussions in Arkansas, 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; radar from the NEXRAD Level II archive.