Alert archive / Louisiana / Mesoscale Discussions in 2017
Mesoscale Discussion 403
The Storm Prediction Center issued this mesoscale discussion at Apr 2, 2017, 12:49 PM CDT for 13 parishes in Louisiana; 13 counties in Mississippi. It was in force for 116 min.
The area
The outline as issued.
The facts
- Issued
- Apr 2, 2017, 12:49 PM CDT (17:49 UTC)
- Expired
- Apr 2, 2017, 2:45 PM CDT
- In force
- 116 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 40%
All 26 counties
Avoyelles Parish, LA, Concordia Parish, LA, East Baton Rouge Parish, LA, East Carroll Parish, LA, East Feliciana Parish, LA, Franklin Parish, LA, Madison Parish, LA, Pointe Coupee Parish, LA, Saint Helena Parish, LA, Saint Landry Parish, LA, Tensas Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Adams County, MS, Amite County, MS, Claiborne County, MS, Copiah County, MS, Franklin County, MS, Hinds County, MS, Issaquena County, MS, Jefferson County, MS, Lawrence County, MS, Lincoln County, MS, Pike County, MS, Warren County, MS, Wilkinson County, MS
The watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Jackson, MS (KJAN), launched 12:00Z, 5.8 hours before the alert went out and 146 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.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 1500 m above ground
- 0-6 km bulk shear
- 30 kt
- 0-1 km storm-relative helicity
- 106 m²/s²
- 0-3 km storm-relative helicity
- 131 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
111
ACUS11 KWNS 021749
SWOMCD
SPC MCD 021749
MSZ000-LAZ000-021945-
Mesoscale Discussion 0403
NWS Storm Prediction Center Norman OK
1249 PM CDT Sun Apr 02 2017
Areas affected...Portions of eastern LA...central/western
MS...southern LA
Concerning...Severe potential...Watch possible
Valid 021749Z - 021945Z
Probability of Watch Issuance...40 percent
SUMMARY...The severe risk will gradually increase east of ongoing
Tornado Watch 109. While not presently likely, these areas will
continue to be monitored for possible watch issuance through
mid-afternoon. The severe risk and watch probabilities will increase
later in the afternoon.
DISCUSSION...Positive theta-e advection in association with a
northward-advancing warm front analyzed from west-central LA to
southern LA continues fostering convective development over
south-central LA. This activity is blossoming over the northern
extent of an uncapped, very moist boundary layer supporting
2000-3000 J/kg of MLCAPE. Lake Charles radar imagery indicates many
cells already exhibiting supercellular characteristics, and this
activity may continue developing northward across areas east of
Tornado Watch 109. Stronger deep ascent remains displaced to the
west of the area, and overall confidence in a more widespread severe
risk is limited in the short term. Nevertheless, with 35-50 kt of
effective shear supporting organized convective structures and
effective SRH of 300-500 m2/s2 building northward, the conditional
risk for severe hail, wind, and tornadoes may exist through
mid-afternoon. By later in the afternoon, as stronger deep ascent
arrives, unconditional severe-thunderstorm and tornado probabilities
will increase.
..Cohen/Hart.. 04/02/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...JAN...LIX...LCH...
LAT...LON 30749220 31059201 31629183 32619163 32889133 32879068
32208994 31299010 30489078 30449183 30749220SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 2, 9:04 AM CDT | Mesoscale Discussion | SPC | Beauregard, Sabine, Vernon | 2 hr |
| Apr 2, 9:05 AM CDT | Mesoscale Discussion | SPC | Acadia, Ascension, East Baton Rouge, Iberville, Lafayette, Livingston and 5 more | 85 min |
| Apr 2, 10:39 AM CDT | Tornado Watch | SPC | Bienville, Bossier, Caddo, Caldwell, Claiborne, De Soto and 13 more | 5 hr |
| Apr 2, 12:22 PM CDT | Mesoscale Discussion | SPC | Sabine | 83 min |
| Apr 2, 1:34 PM CDT | Tornado Watch | SPC | Acadia, Allen, Avoyelles, Beauregard, Bienville, Calcasieu and 28 more | 7 hr |
| Apr 2, 2:06 PM CDT | Mesoscale Discussion | SPC | Grant, LaSalle, Natchitoches, Rapides, Sabine, Vernon and 1 more | 54 min |
| Apr 2, 3:08 PM CDT | Mesoscale Discussion | SPC | Ascension, East Baton Rouge, East Feliciana, Livingston, Saint Charles, Saint Helena and 6 more | 3 hr |
| Apr 2, 3:13 PM CDT | Mesoscale Discussion | SPC | Allen, Avoyelles, Beauregard, Caldwell, Catahoula, Concordia and 13 more | 92 min |
| Apr 2, 4:52 PM CDT | Tornado Watch | SPC | Ascension, Concordia, East Baton Rouge, East Feliciana, Iberville, Livingston and 8 more | 9 hr |
| Apr 2, 5:54 PM CDT | Mesoscale Discussion | SPC | Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Catahoula and 7 more | 96 min |
| Apr 2, 3:31 PM CDT | Mesoscale Discussion | SPC | Carroll, Holmes, Humphreys, Leflore, Montgomery, Sunflower and 1 more | 29 min |
| Apr 2, 5:06 PM CDT | Mesoscale Discussion | SPC | Bolivar, Calhoun, Chickasaw, Coahoma, Grenada, Itawamba and 9 more | 84 min |
| Apr 2, 5:26 PM CDT | Severe Thunderstorm Watch | SPC | Calhoun, Chickasaw, Coahoma, Itawamba, Lafayette, Lee and 7 more | 3 hr |
Nearby
Mesoscale Discussions in Louisiana, 2017Mesoscale Discussions in Mississippi, 2017Every 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.