Alert archive / Mississippi / Mesoscale Discussions in 2021
Mesoscale Discussion 109
The Storm Prediction Center issued this mesoscale discussion at Feb 17, 2021, 10:53 AM CST for Ashley County, Chicot County, Arkansas; 26 parishes in Louisiana; 52 counties in Mississippi. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Feb 17, 2021, 10:53 AM CST (16:53 UTC)
- Expired
- Feb 17, 2021, 5:00 PM CST
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Freezing rain
All 80 counties
Ashley County, AR, Chicot County, AR, Avoyelles Parish, LA, Bienville Parish, LA, Caldwell Parish, LA, Catahoula Parish, LA, Claiborne Parish, LA, Concordia Parish, LA, East Carroll Parish, LA, Franklin Parish, LA, Grant Parish, LA, Jackson Parish, LA, LaSalle Parish, LA, Lincoln Parish, LA, Madison Parish, LA, Morehouse Parish, LA, Natchitoches Parish, LA, Ouachita Parish, LA, Rapides Parish, LA, Red River Parish, LA, Richland Parish, LA, Sabine Parish, LA, Tensas Parish, LA, Union Parish, LA, Vernon Parish, LA, Webster Parish, LA, West Carroll Parish, LA, Winn Parish, LA, Adams County, MS, Attala County, MS, Calhoun County, MS, Carroll County, MS, Chickasaw County, MS, Choctaw County, MS, Claiborne County, MS, Clarke County, MS, Clay County, MS, Copiah County, MS, Covington County, MS, Franklin County, MS, Grenada County, MS, Hinds County, MS, Holmes County, MS, Humphreys County, MS, Issaquena County, MS, Itawamba 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, Lee County, MS, Leflore County, MS, Lincoln County, MS, Lowndes County, MS, Madison County, MS, Monroe County, MS, Montgomery County, MS, Neshoba County, MS, Newton County, MS, Noxubee County, MS, Oktibbeha County, MS, Pontotoc County, MS, Rankin County, MS, Scott County, MS, Sharkey County, MS, Simpson County, MS, Smith County, MS, Sunflower County, MS, Tallahatchie County, MS, Union County, MS, Warren County, MS, Washington County, MS, Webster County, MS, Winston County, MS, Yalobusha County, MS, Yazoo County, MS
The radar
The Jackson/Brandon,MS radar (KDGX), 88 km from the middle of the area, began a volume at 16:56 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 12:00Z, 4.9 hours before the alert went out and 78 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
- 1328 m above ground
- 0-6 km bulk shear
- 92 kt
- 0-1 km storm-relative helicity
- 182 m²/s²
- 0-3 km storm-relative helicity
- 249 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
758
ACUS11 KWNS 171653
SWOMCD
SPC MCD 171653
ALZ000-MSZ000-ARZ000-LAZ000-TXZ000-172300-
Mesoscale Discussion 0109
NWS Storm Prediction Center Norman OK
1053 AM CST Wed Feb 17 2021
Areas affected...northern/central Louisiana into much of Mississippi
Concerning...Freezing rain
Valid 171653Z - 172300Z
SUMMARY...Areas of moderate to heavy freezing rain will persist
across Louisiana today while expanding eastward into Mississippi
this afternoon.
DISCUSSION...A large shield of precipitation continues across much
of Louisiana and eastern Texas currently. The precipitation is
enhanced by strong low-level flow (with 50-55kts of southerly flow
indicated in the 1-2km layer at HGX) and isentropic lift atop a
shallow, cold airmass residing across the region. Meanwhile, light
northeasterly surface trajectories will help in maintaining a
shallow, sub-freezing airmass across much of the discussion area
over the next several hours. Upstream observations have indicated
up to .25 inch per hour of freezing rain rates in heavier bands.
0.05 to 0.20 inch per hour freezing rain rates will be possible in
many areas through 21Z, though precipitation may taper across
western Louisiana around that time as forcing for ascent (attendant
to the stronger low-level flow) shifts east of the area. On the
southern end of the discussion area, freezing rain may change over
to rain later this afternoon as warm advection erodes the
near-surface cool layer.
..Cook.. 02/17/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BMX...MOB...MEG...JAN...LIX...LZK...LCH...SHV...
LAT...LON 30859307 31119353 31779369 32659344 33039299 33179242
33519145 33849061 34088997 34578897 34618857 34428833
34148817 33878817 32728832 32238841 31638895 31399040
31139165 30859307SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Feb 17, 9:15 AM CST | Mesoscale Discussion | SPC | Arkansas, Bradley, Calhoun, Clark, Cleveland, Columbia and 28 more | 6 hr |
| Feb 17, 3:22 PM CST | Mesoscale Discussion | SPC | Arkansas, Calhoun, Clark, Cleveland, Crittenden, Cross and 23 more | 4 hr |
| Feb 17, 1:55 AM CST | Mesoscale Discussion | SPC | Allen, Beauregard, Calcasieu, Sabine, Vernon | 6 hr |
| Feb 17, 7:38 AM CST | Mesoscale Discussion | SPC | Allen, Avoyelles, Beauregard, Caldwell, Catahoula, Concordia and 10 more | 4 hr |
| Feb 17, 5:38 PM CST | Mesoscale Discussion | SPC | Jefferson, Lafourche, Orleans, Plaquemines, Saint Bernard, Saint Charles and 1 more | 3 hr |
| Feb 17, 1:00 PM CST | Mesoscale Discussion | SPC | Alcorn, Benton, Itawamba, Lafayette, Lee, Marshall and 6 more | 3 hr |
Nearby
Mesoscale Discussions in Mississippi, 2021Mesoscale Discussions in Louisiana, 2021Mesoscale Discussions in Arkansas, 2021Every mesoscale discussion in 2021
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.