Alert archive / Louisiana / Mesoscale Discussions in 2021
Mesoscale Discussion 18
The Storm Prediction Center issued this mesoscale discussion at Jan 10, 2021, 5:38 PM CST for 7 parishes in Louisiana; Nacogdoches County, San Augustine County, Shelby County, Texas. It was in force for 4 hr.
The area
The outline as issued.
The facts
- Issued
- Jan 10, 2021, 5:38 PM CST (23:38 UTC)
- Expired
- Jan 10, 2021, 9:45 PM CST
- In force
- 4 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Heavy snow
Counties Bienville Parish, LA, De Soto Parish, LA, Jackson Parish, LA, Natchitoches Parish, LA, Red River Parish, LA, Sabine Parish, LA, Winn Parish, LA, Nacogdoches County, TX, San Augustine County, TX, Shelby County, TX
The radar
The Shreveport radar (KSHV), 61 km from the middle of the area, began a volume at 23:39 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, 11.6 hours before the alert went out and 65 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
- 844 m above ground
- 0-6 km bulk shear
- 31 kt
- 0-1 km storm-relative helicity
- -74 m²/s²
- 0-3 km storm-relative helicity
- 5 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
021 ACUS11 KWNS 102339 SWOMCD SPC MCD 102338 LAZ000-TXZ000-110345- Mesoscale Discussion 0018 NWS Storm Prediction Center Norman OK 0538 PM CST Sun Jan 10 2021 Areas affected...Portions of eastern Texas and northern Louisiana Concerning...Heavy snow Valid 102338Z - 110345Z SUMMARY...A corridor of locally heavy snow, with up to 1 inch per hour snow rates, will be noted from east Texas into northern Louisiana. DISCUSSION...Center of upper low is currently located just west of SEP. This feature is forecast to shift into northeast TX overnight with the primary precipitation shield expected to focus from the upper TX coast into LA through the early morning hours. Large-scale forcing/cooling is spreading across east TX into northern LA which has allowed heavier snow rates aloft to gradually cool the boundary layer, allowing snow to reach the surface as far east as Grant Parish LA. While pockets/bands of locally heavy snow currently extend southwest of this region into Walker County TX, radar trends suggest a more extended precipitation event will be noted just downstream into northern LA into the late-evening hours. Snow rates may approach 1 inch per hour in the heavier bands. ..Darrow.. 01/10/2021 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...SHV... LAT...LON 32039498 32419267 32099212 31649313 31209483 32039498
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jan 10, 4:14 AM CST | Mesoscale Discussion | SPC | Borden, Callahan, Coke, Coleman, Dawson, Fisher and 12 more | 4 hr |
| Jan 10, 9:34 AM CST | Mesoscale Discussion | SPC | Bell, Bosque, Brown, Callahan, Coleman, Comanche and 19 more | 4 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.