Alert archive / Mississippi / Mesoscale Discussions in 2017
Mesoscale Discussion 83
The Storm Prediction Center issued this mesoscale discussion at Jan 20, 2017, 10:44 PM CST for 18 parishes in Louisiana; 23 counties in Mississippi. It was in force for 61 min.
The area
The outline as issued.
The facts
- Issued
- Jan 20, 2017, 10:44 PM CST (04:44 UTC)
- Expired
- Jan 20, 2017, 11:45 PM CST
- In force
- 61 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 95%
All 41 counties
Ascension Parish, LA, Assumption Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Jefferson Parish, LA, Lafourche Parish, LA, Livingston Parish, LA, Orleans 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, Washington Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Adams County, MS, Amite 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, Jefferson Davis County, MS, Jones County, MS, Lamar County, MS, Lawrence County, MS, Lincoln County, MS, Marion County, MS, Pearl River County, MS, Perry County, MS, Pike County, MS, Simpson County, MS, Stone County, MS, Walthall 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
Slidell Radar S, LA (KSIL), launched 00:00Z, 4.7 hours before the alert went out and 58 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.
063
ACUS11 KWNS 210444
SWOMCD
SPC MCD 210444
MSZ000-LAZ000-210545-
Mesoscale Discussion 0083
NWS Storm Prediction Center Norman OK
1044 PM CST Fri Jan 20 2017
Areas affected...southeast Louisiana through southern Mississippi
Concerning...Severe potential...Watch needed soon
Valid 210444Z - 210545Z
Probability of Watch Issuance...95 percent
SUMMARY...Threat for a few tornadoes, damaging wind and large hail
will gradually expand east into southeast LA and southern MS through
the early morning hours. A tornado watch will be issued by around
05Z.
DISCUSSION...Late this evening a warm front extends from near the
Gulf Coast through southern LA. This boundary will move slowly north
through the early morning as the low-level jet strengthens in
response to a northeastward-ejecting shortwave trough. Northward
advection of richer low-level moisture and eastward expansion of
elevated mixed layer plume will destabilize the atmosphere
downstream from storms currently developing from southwest through
south-central LA. The destabilization process, increasing low-level
hodograph size and strong effective bulk shear will promote
supercells and bowing segments as storms continue east. Greatest
tornado threat may be as storms interact with warm front. Otherwise,
large hail and damaging wind will also be likely.
..Dial/Edwards.. 01/21/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MOB...JAN...LIX...
LAT...LON 31798874 30848847 29678915 29258993 29359078 30159122
30569154 31439162 32019022 31798874SPC 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, 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, 2:55 AM CST | Mesoscale Discussion | SPC | Ascension, Assumption, East Baton Rouge, East Feliciana, Iberville, Jefferson and 16 more | 2 hr |
| 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.