Alert archive / Louisiana / Mesoscale Discussions in 2017
Mesoscale Discussion 182
The Storm Prediction Center issued this mesoscale discussion at Feb 14, 2017, 2:02 PM CST for 26 parishes in Louisiana; 16 counties in Mississippi. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Feb 14, 2017, 2:02 PM CST (20:02 UTC)
- Expired
- Feb 14, 2017, 4:30 PM CST
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 20%
All 42 counties
Ascension Parish, LA, Assumption Parish, LA, Avoyelles Parish, LA, Catahoula Parish, LA, Concordia Parish, LA, East Baton Rouge Parish, LA, East Carroll Parish, LA, East Feliciana Parish, LA, Franklin Parish, LA, Iberville Parish, LA, Lafayette Parish, LA, LaSalle Parish, LA, Livingston Parish, LA, Madison 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 Landry Parish, LA, Saint Martin Parish, LA, St. Mary Parish, LA, Tangipahoa 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, Madison County, MS, Pike County, MS, Sharkey County, MS, Warren County, MS, Wilkinson County, MS, Yazoo County, MS
The nearest sounding before it
Slidell Radar S, LA (KSIL), launched 12:00Z, 8.0 hours before the alert went out and 165 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
- 989 m above ground
- 0-6 km bulk shear
- 31 kt
- 0-1 km storm-relative helicity
- 87 m²/s²
- 0-3 km storm-relative helicity
- 153 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
486
ACUS11 KWNS 142002
SWOMCD
SPC MCD 142002
MSZ000-LAZ000-142230-
Mesoscale Discussion 0182
NWS Storm Prediction Center Norman OK
0202 PM CST Tue Feb 14 2017
Areas affected...Portions of southern/eastern
LA...western/central/southern MS
Concerning...Severe potential...Watch unlikely
Valid 142002Z - 142230Z
Probability of Watch Issuance...20 percent
SUMMARY...Areas east of Tornado Watch 33 are being monitored for
isolated severe potential this afternoon. Present indications are
that additional/downstream Watch issuance is unlikely.
DISCUSSION...Substantial weakening has been noted with a convective
line crossing parts of western LA. As the broader precipitation
pattern associated with this MCS has transitioned from
trailing-stratiform to leading-stratiform, warm-sector
destabilization attendant to 1007-mb surface low analyzed in
northwest LA has been restricted. Furthermore, the 18Z Slidell LA
sounding indicates that the low levels north of the immediate Gulf
Coast are only modestly moist, with a lowest-100-mb mean mixing
ratio of 10.8 g/kg. Surface dewpoints have mixed out into the upper
50s to around 60F across many parts of central/southern MS and
southern LA where insolation has occurred peripheral to denser
MCS-related cloud canopies. As such, observational trends suggest
that inland destabilization remains quite muted ahead of any remnant
convection accompanying the MCS, and this activity may pose only
marginal/isolated severe potential through late afternoon as it
spreads across parts of the Lower MS Valley region.
Regardless, a well-defined surge of drying is evident on the upshear
side of the MCS -- based on the larger-scale bowed precipitation
pattern accompanying the aforementioned activity. The related
augmentation of a midlevel speed maximum by the remnant mesoscale
circulation may provide sufficient wind fields for conditional and
isolated damaging-wind potential if any more robust convective cores
were to evolve in the strongly sheared environment. Areas of partial
insolation -- especially from central MS to southeast LA -- may have
boosted low-level lapse rates sufficiently to support such
potential. Somewhat richer Gulf moisture just offshore may be
advected inland with time, and this could eventually translate to a
modest increase in severe potential near the coast. However,
substantial uncertainty in these scenarios remains.
..Cohen/Hart.. 02/14/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...JAN...LIX...LCH...SHV...
LAT...LON 29659196 30739218 31959224 32829129 33089055 32878994
30799014 29659028 29349097 29659196SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Feb 14, 7:21 AM CST | Mesoscale Discussion | SPC | Acadia, Allen, Beauregard, Calcasieu, Cameron, Evangeline and 3 more | 114 min |
| Feb 14, 9:38 AM CST | Tornado Watch | SPC | Acadia, Allen, Beauregard, Calcasieu, Cameron, Evangeline and 5 more | 5 hr |
| Feb 14, 11:15 AM CST | Mesoscale Discussion | SPC | Acadia, Allen, Beauregard, Calcasieu, Cameron, Jefferson Davis and 2 more | 90 min |
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.