Alert archive / Louisiana / Mesoscale Discussions in 2021
Mesoscale Discussion 107
The Storm Prediction Center issued this mesoscale discussion at Feb 17, 2021, 7:38 AM CST for 16 parishes in Louisiana; Jasper County, Newton County, Sabine County, Texas. It was in force for 4 hr.
The area
The outline as issued.
The facts
- Issued
- Feb 17, 2021, 7:38 AM CST (13:38 UTC)
- Expired
- Feb 17, 2021, 11:45 AM CST
- In force
- 4 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Freezing rain
Counties Allen Parish, LA, Avoyelles Parish, LA, Beauregard Parish, LA, Caldwell Parish, LA, Catahoula Parish, LA, Concordia Parish, LA, Franklin Parish, LA, Grant Parish, LA, Jackson Parish, LA, LaSalle Parish, LA, Natchitoches Parish, LA, Rapides Parish, LA, Sabine Parish, LA, Tensas Parish, LA, Vernon Parish, LA, Winn Parish, LA, Jasper County, TX, Newton County, TX, Sabine County, TX
The radar
The Ft Polk radar (KPOE), 28 km from the middle of the area, began a volume at 13:41 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
Shreveport, LA (KSHV), launched 12:00Z, 1.6 hours before the alert went out and 140 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
- 487 m above ground
- 0-6 km bulk shear
- 96 kt
- 0-1 km storm-relative helicity
- 405 m²/s²
- 0-3 km storm-relative helicity
- 463 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
624
ACUS11 KWNS 171339
SWOMCD
SPC MCD 171338
MSZ000-LAZ000-TXZ000-171745-
Mesoscale Discussion 0107
NWS Storm Prediction Center Norman OK
0738 AM CST Wed Feb 17 2021
Areas affected...far east TX...southwest into west-central and
northeast LA
Concerning...Freezing rain
Valid 171338Z - 171745Z
SUMMARY...Heavy freezing rain rates are forecast to develop and
spread into central LA over the next few hours. Rates 0.10 to 0.30
inch per 3 hours are probable.
DISCUSSION...Radar mosaic at 730am CST shows an expanding
precipitation shield across southeast/east TX moving into western
portions of LA. Strengthening low-level warm air advection atop a
shallow sub-freezing layer is providing ample lift. The 6am CST
Lake Charles raob showed a vertical profile supporting freezing
rain, whereas Shreveport farther north where the cold air is deeper
near the surface, supports mainly a sleet/freezing rain mixture.
Surface observations over east TX the past few hours have recorded
varying liquid-equivalent precipitation amounts. Lufkin was located
in a heavier precipitation band and recorded 0.25 inch in 1 hour
between 6-7am CST. Expecting the continuation of moderate to
locally heavy freezing rain rates through the late morning as the
precipitation develops east-northeast across LA. Some of the
heavier bursts of freezing rain may be augmented by convection.
..Smith.. 02/17/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...JAN...LCH...SHV...
LAT...LON 31729388 32429254 32419158 32039118 31359160 30249321
30249378 30749409 31209407 31729388SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Feb 17, 1:55 AM CST | Mesoscale Discussion | SPC | Allen, Beauregard, Calcasieu, Sabine, Vernon | 6 hr |
| Feb 17, 10:53 AM CST | Mesoscale Discussion | SPC | Avoyelles, Bienville, Caldwell, Catahoula, Claiborne, Concordia and 20 more | 6 hr |
| Feb 17, 5:38 PM CST | Mesoscale Discussion | SPC | Jefferson, Lafourche, Orleans, Plaquemines, Saint Bernard, Saint Charles and 1 more | 3 hr |
| Feb 16, 6:59 PM CST | Mesoscale Discussion | SPC | Armstrong, Briscoe, Carson, Castro, Childress, Collingsworth and 7 more | 4 hr |
| Feb 16, 8:14 PM CST | Mesoscale Discussion | SPC | Archer, Clay, Cooke, Grayson, Jack, Montague and 2 more | 4 hr |
| Feb 16, 9:41 PM CST | Mesoscale Discussion | SPC | Bell, Brazos, Burleson, Burnet, Falls, Lampasas and 5 more | 4 hr |
| Feb 17, 9:15 AM CST | Mesoscale Discussion | SPC | Bowie, Cass | 6 hr |
Nearby
Mesoscale Discussions in Louisiana, 2021Mesoscale Discussions in Texas, 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.