Alert archive / Mississippi / Mesoscale Discussions in 2017
Mesoscale Discussion 99
The Storm Prediction Center issued this mesoscale discussion at Jan 21, 2017, 8:22 PM CST for 8 counties in Arkansas; 19 parishes in Louisiana; 36 counties in Mississippi. It was in force for 113 min.
The area
The outline as issued.
The facts
- Issued
- Jan 21, 2017, 8:22 PM CST (02:22 UTC)
- Expired
- Jan 21, 2017, 10:15 PM CST
- In force
- 113 min
- Issued by
- the Storm Prediction Center
All 63 counties
Ashley County, AR, Bradley County, AR, Calhoun County, AR, Chicot County, AR, Cleveland County, AR, Desha County, AR, Drew County, AR, Union County, AR, Bienville Parish, LA, Caldwell Parish, LA, Catahoula Parish, LA, Claiborne Parish, LA, Concordia Parish, LA, East Carroll Parish, LA, Franklin Parish, LA, Jackson Parish, LA, LaSalle Parish, LA, Lincoln Parish, LA, Madison Parish, LA, Morehouse Parish, LA, Ouachita Parish, LA, Richland Parish, LA, Tensas Parish, LA, Union Parish, LA, Webster Parish, LA, West Carroll Parish, LA, Winn Parish, LA, Adams County, MS, Attala County, MS, Bolivar County, MS, Carroll County, MS, Claiborne County, MS, Clarke County, MS, Copiah County, MS, Covington County, MS, Franklin County, MS, Hinds County, MS, Holmes County, MS, Humphreys County, MS, Issaquena County, MS, Jasper County, MS, Jefferson County, MS, Jefferson Davis County, MS, Jones County, MS, Kemper County, MS, Lauderdale County, MS, Lawrence County, MS, Leake County, MS, Leflore County, MS, Lincoln County, MS, Madison County, MS, Neshoba County, MS, Newton County, MS, Rankin County, MS, Scott County, MS, Sharkey County, MS, Simpson County, MS, Smith County, MS, Sunflower County, MS, Warren County, MS, Washington County, MS, Winston County, MS, Yazoo County, MS
The radar
The Jackson/Brandon,MS radar (KDGX), 110 km from the middle of the area, began a volume at 02:23 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
The nearest sounding before it
Jackson, MS (KJAN), launched 00:00Z, 2.4 hours before the alert went out and 101 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
- 1036 J/kg
- Mixed-layer CIN
- -131 J/kg
- Mixed-layer LCL
- 1052 m above ground
- 0-6 km bulk shear
- 63 kt
- 0-1 km storm-relative helicity
- 144 m²/s²
- 0-3 km storm-relative helicity
- 155 m²/s²
- Significant tornado parameter
- 0.4
- Supercell composite
- 1.8
The text
As transmitted.
757
ACUS11 KWNS 220222
SWOMCD
SPC MCD 220222
MSZ000-ARZ000-LAZ000-220415-
Mesoscale Discussion 0099
NWS Storm Prediction Center Norman OK
0822 PM CST Sat Jan 21 2017
Areas affected...Portions of northern Louisiana...southern
Arkansas...and central/southern Mississippi
Concerning...Tornado Watch 17...18...
Valid 220222Z - 220415Z
The severe weather threat for Tornado Watch 17, 18 continues.
SUMMARY...Severe thunderstorms will continue to develop into Watch
18 over the next hour. Across northern portions of the watch, the
main severe hazard will likely transition to damaging winds (with a
tornado or two possible). Farther southeast in Mississippi, a
greater tornado/large-hail potential will exist, with a strong
tornado possible.
DISCUSSION...In response to increasing warm advection related to the
low-level jet, severe thunderstorms near the LA/AR border have begun
to grow upscale into a broken band, with embedded mesocyclones still
noted. This evolution should continue as the storms progress into
Watch 18, resulting in damaging winds likely becoming the dominant
threat across northern portions of the watch. A tornado or two will
still be possible, however, considering the amplifying low-level
flow and notable veering with height of 0-3-km winds.
Farther southeast over south-central Mississippi, dew points in the
lower 60s will favor slightly greater surface-based buoyancy. KDGX
VWP data suggest around 250-300 m2/s2 of storm-relative helicity is
present for low-level mesocyclone organization. With increasing
semi-discrete convection over the next several hours, the tornado
potential should rise accordingly, and a strong tornado (primarily
closer to the MS/AL border) cannot be ruled out.
..Picca.. 01/22/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MOB...MEG...JAN...LIX...LZK...SHV...
LAT...LON 32099280 32719344 33029341 33969225 33749036 32938851
32258847 31648881 31278954 31399119 31489220 32099280SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jan 21, 7:50 PM CST | Tornado Watch | SPC | Ashley, Bradley, Chicot, Cleveland, Desha, Drew and 1 more | 4 hr |
| Jan 21, 6:05 PM CST | Mesoscale Discussion | SPC | Ascension, Assumption, Avoyelles, Catahoula, Concordia, East Baton Rouge and 22 more | 85 min |
| Jan 21, 8:14 PM CST | Mesoscale Discussion | SPC | East Feliciana, Livingston, Saint Helena, Saint Tammany, Tangipahoa, Washington and 1 more | 61 min |
| Jan 21, 6:51 PM CST | Tornado Watch | SPC | George, Greene, Perry, Stone, Wayne | 8 hr |
| Jan 21, 8:30 PM CST | Mesoscale Discussion | SPC | Wayne | 90 min |
| Jan 21, 9:57 PM CST | Mesoscale Discussion | SPC | Wayne | 93 min |
Nearby
Mesoscale Discussions in Mississippi, 2017Mesoscale Discussions in Louisiana, 2017Mesoscale Discussions in Arkansas, 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; radar from the NEXRAD Level II archive.