Alert archive / Louisiana / Mesoscale Discussions in 2017
Mesoscale Discussion 897
The Storm Prediction Center issued this mesoscale discussion at May 28, 2017, 10:59 AM CDT for 4 states. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- May 28, 2017, 10:59 AM CDT (15:59 UTC)
- Expired
- May 28, 2017, 1:00 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 20%
All 38 counties
Baldwin County, AL, Covington County, AL, Escambia County, AL, Geneva County, AL, Mobile County, AL, Escambia County, FL, Holmes County, FL, Okaloosa County, FL, Santa Rosa County, FL, Walton County, FL, Washington County, FL, Ascension Parish, LA, Assumption Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Davis Parish, LA, Jefferson Parish, LA, Lafayette Parish, LA, Lafourche Parish, LA, Orleans Parish, LA, Plaquemines Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Martin Parish, LA, Saint Tammany Parish, LA, St. Mary Parish, LA, Terrebonne Parish, LA, Vermilion Parish, LA, George County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Pearl River County, MS, Stone County, MS
The nearest sounding before it
Slidell Radar S, LA (KSIL), launched 12:00Z, 4.0 hours before the alert went out and 13 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
- 2549 J/kg
- Mixed-layer CIN
- -50 J/kg
- Mixed-layer LCL
- 632 m above ground
- 0-6 km bulk shear
- 12 kt
- 0-1 km storm-relative helicity
- -39 m²/s²
- 0-3 km storm-relative helicity
- -24 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
442
ACUS11 KWNS 281600
SWOMCD
SPC MCD 281559
FLZ000-ALZ000-MSZ000-LAZ000-281800-
Mesoscale Discussion 0897
NWS Storm Prediction Center Norman OK
1059 AM CDT Sun May 28 2017
Areas affected...Parts of southern
Louisiana/Mississippi/Alabama/Georgia and the Florida panhandle
Concerning...Severe potential...Watch unlikely
Valid 281559Z - 281800Z
Probability of Watch Issuance...20 percent
SUMMARY...Intensifying thunderstorm development is expected across
southern portions of the central Gulf states and associated coastal
areas through 18-21Z. This probably will be accompanied by at least
some localized severe weather potential. It is not yet clear that a
watch will be needed, but trends will be monitored.
DISCUSSION...Forcing for ascent along the leading edge of outflows
associated with extensive overnight convective development is
maintaining a narrow corridor of sustained thunderstorm development.
The composite outflow boundary has been steadily advancing
southward, and appears likely to progress south of the stronger
westerlies, toward Gulf coastal areas, through 18-21Z. However,
mid-level height falls and the southward suppression of a lingering
plume of warm elevated mixed layer air, coupled with insolation, are
contributing to weakening of inhibition for seasonably moist
boundary layer air ahead of activity. This may lead to a general
intensification of thunderstorm development during the next few
hours, with locally enhanced convergence along the composite outflow
boundary eventually supporting some rapid intensification in the
presence of moderate to large CAPE (on the order of 2000-4000 J/kg).
This degree of latent instability is being supported by steep
mid-level lapse rates, which probably will contribute to
thermodynamic profiles conducive to frequent lightning, some severe
hail, and locally strong downbursts in the most vigorous storms.
Strengthening of the larger-scale cold pool may also support
increasing gusts along its leading edge which could approach severe
levels by mid to late afternoon.
..Kerr/Hart.. 05/28/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...TAE...MOB...JAN...LIX...LCH...
LAT...LON 30439358 30289242 30379090 30619022 31018928 31128769
31258685 31518609 30698540 30208585 29898794 29298924
29149078 29379320 29709376 30439358SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 27, 9:07 PM CDT | Severe Thunderstorm Watch | SPC | Blount, Cherokee, Colbert, Cullman, DeKalb, Etowah and 13 more | 8 hr |
| May 27, 11:46 PM CDT | Mesoscale Discussion | SPC | Bibb, Calhoun, Clay, Cleburne, Fayette, Jefferson and 8 more | 59 min |
| May 28, 2:11 AM CDT | Mesoscale Discussion | SPC | Bibb, Blount, Calhoun, Cherokee, Clay, Cleburne and 23 more | 2 hr |
| May 28, 2:53 AM CDT | Severe Thunderstorm Watch | SPC | Calhoun, Chambers, Chilton, Clay, Cleburne, Coosa and 6 more | 4 hr |
| May 28, 2:53 AM CDT | Mesoscale Discussion | SPC | Bossier, Caddo, Claiborne, Lincoln, Union, Webster | 2 hr |
| May 28, 5:01 PM CDT | Mesoscale Discussion | SPC | Bienville, Bossier, Caddo, Caldwell, Claiborne, De Soto and 9 more | 59 min |
| May 28, 5:19 PM CDT | Severe Thunderstorm Watch | SPC | Bienville, Bossier, Caddo, Caldwell, Claiborne, De Soto and 11 more | 4 hr |
| May 27, 9:26 PM CDT | Mesoscale Discussion | SPC | DeSoto | 94 min |
| May 27, 9:59 PM CDT | Tornado Watch | SPC | Alcorn, Benton, DeSoto, Itawamba, Lafayette, Lee and 9 more | 2 hr |
| May 28, 12:18 AM CDT | Severe Thunderstorm Watch | SPC | Alcorn, Benton, Bolivar, Calhoun, Carroll, Chickasaw and 27 more | 6 hr |
| May 28, 4:59 AM CDT | Mesoscale Discussion | SPC | Bolivar, Coahoma, Humphreys, Leflore, Sunflower, Washington | 2 hr |
Nearby
Mesoscale Discussions in Louisiana, 2017Mesoscale Discussions in Florida, 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.