Alert archive / Mississippi / Mesoscale Discussions in 2017
Mesoscale Discussion 85
The Storm Prediction Center issued this mesoscale discussion at Jan 21, 2017, 2:55 AM CST for 22 parishes in Louisiana; 35 counties in Mississippi. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Jan 21, 2017, 2:55 AM CST (08:55 UTC)
- Expired
- Jan 21, 2017, 5:00 AM CST
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
All 57 counties
Ascension Parish, LA, Assumption Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Iberville Parish, LA, Jefferson Parish, LA, Lafourche Parish, LA, Livingston Parish, LA, Orleans Parish, LA, Plaquemines Parish, LA, Pointe Coupee Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint Helena Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Tammany Parish, LA, Tangipahoa Parish, LA, Terrebonne Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Adams County, MS, Amite County, MS, Clarke County, MS, Copiah County, MS, Covington County, MS, Forrest County, MS, Franklin County, MS, George County, MS, Greene County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Jasper County, MS, Jefferson County, MS, Jefferson Davis County, MS, Jones County, MS, Kemper County, MS, Lamar County, MS, Lauderdale County, MS, Lawrence County, MS, Lincoln County, MS, Marion County, MS, Neshoba County, MS, Newton County, MS, Pearl River County, MS, Perry County, MS, Pike County, MS, Rankin County, MS, Scott County, MS, Simpson County, MS, Smith County, MS, Stone County, MS, Walthall County, MS, Wayne County, MS, Wilkinson County, MS
The nearest sounding before it
Slidell Radar S, LA (KSIL), launched 00:00Z, 8.9 hours before the alert went out and 34 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
- 628 J/kg
- Mixed-layer CIN
- -28 J/kg
- Mixed-layer LCL
- 857 m above ground
- 0-6 km bulk shear
- 45 kt
- 0-1 km storm-relative helicity
- 85 m²/s²
- 0-3 km storm-relative helicity
- 150 m²/s²
- Significant tornado parameter
- 0.2
- Supercell composite
- 1.6
The text
As transmitted.
392
ACUS11 KWNS 210856
SWOMCD
SPC MCD 210855
ALZ000-MSZ000-LAZ000-211100-
Mesoscale Discussion 0085
NWS Storm Prediction Center Norman OK
0255 AM CST Sat Jan 21 2017
Areas affected...Southeast Louisiana and southern Mississippi
Concerning...Tornado Watch 10...
Valid 210855Z - 211100Z
The severe weather threat for Tornado Watch 10 continues.
SUMMARY...Severe weather including a tornado threat will persist
across southeast Louisiana and southern Mississippi during the
overnight. The greatest threat for tornadoes in the short term is
expected to be from the vicinity of BTR and eastward from Hammond,
LA to Hattiesburg, MS with the increase in supercell development.
DISCUSSION...Recent surface analyses /06-08Z/ indicated a developing
mesolow, now located near BTR, with the strongest pressure falls
from BTR to MCB, while this region and into southwest and
south-central MS also has the coldest cloud tops and greatest
lightning coverage/density. The mesolow is expected to track to the
east-northeast along a northward-developing warm front through
southern MS to central AL (near or just south of a TCL-BHM line) per
trends in mesoanalyses and HRRR forecasts. Forcing for ascent
associated with a progressive and compact shortwave trough moving
into Louisiana at this time will sustain a low-level mass response
across and downstream from WW 10. This response is being observed
per backed southerly low-level winds with an associated increase in
low-level moistening and warm air advection. These factors will
further aid in the development of additional thunderstorms east of
the main BTR-MCB storm complex into southeast MS and southwest AL
through the overnight.
Further strengthening of vertically veering wind profiles and
increasing deep-layer ascent per an apparent coupled jet structure
with the progressive trough suggest supercells should increase in
coverage and intensity across WW 10.
..Peters.. 01/21/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BMX...MOB...JAN...LIX...LCH...
LAT...LON 29449124 30539175 31379168 31879103 32518987 32928915
32928835 31048845 29848835 29078862 28828910 28718955
28858997 28779109 29179122 29449124SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jan 20, 6:37 PM CST | Mesoscale Discussion | SPC | Acadia, Allen, Beauregard, Calcasieu, Cameron, Evangeline and 3 more | 113 min |
| Jan 20, 7:32 PM CST | Tornado Watch | SPC | Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 9 more | 6 hr |
| Jan 20, 10:04 PM CST | Mesoscale Discussion | SPC | Acadia, Allen, Avoyelles, Calcasieu, Cameron, Evangeline and 7 more | 116 min |
| Jan 20, 10:44 PM CST | Mesoscale Discussion | SPC | Ascension, Assumption, East Baton Rouge, East Feliciana, Jefferson, Lafourche and 12 more | 61 min |
| Jan 20, 11:00 PM CST | Tornado Watch | SPC | Ascension, Assumption, Concordia, East Baton Rouge, East Feliciana, Iberville and 17 more | 8 hr |
| Jan 21, 1:41 AM CST | Mesoscale Discussion | SPC | Acadia, Avoyelles, Cameron, Evangeline, Iberia, Jefferson Davis and 5 more | 64 min |
| Jan 21, 6:35 AM CST | Mesoscale Discussion | SPC | Jefferson, Lafourche, Orleans, Plaquemines, Saint Bernard, Saint Charles and 1 more | 55 min |
| Jan 21, 2:33 PM CST | Mesoscale Discussion | SPC | Bienville, Bossier, Caddo, Claiborne, De Soto, Jackson and 8 more | 2 hr |
| Jan 21, 2:34 PM CST | Mesoscale Discussion | SPC | Allen, Ascension, Avoyelles, Catahoula, Concordia, East Baton Rouge and 16 more | 2 hr |
| Jan 21, 3:29 PM CST | Tornado Watch | SPC | Acadia, Ascension, Avoyelles, Catahoula, Concordia, East Baton Rouge and 22 more | 6 hr |
| Jan 21, 3:41 PM CST | Tornado Watch | SPC | Bienville, Bossier, Caddo, Caldwell, Claiborne, De Soto and 11 more | 7 hr |
| Jan 21, 5:32 PM CST | Mesoscale Discussion | SPC | Avoyelles, Bienville, Bossier, Caddo, Caldwell, Catahoula and 23 more | 118 min |
Nearby
Mesoscale Discussions in Mississippi, 2017Mesoscale Discussions in Louisiana, 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.