Alert archive / Texas / Mesoscale Discussions in 2021
Mesoscale Discussion 84
The Storm Prediction Center issued this mesoscale discussion at Feb 15, 2021, 1:08 AM CST for 9 counties in Arkansas; 9 parishes in Louisiana; 33 counties in Texas. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Feb 15, 2021, 1:08 AM CST (07:08 UTC)
- Expired
- Feb 15, 2021, 7:15 AM CST
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Heavy snow
All 51 counties
Calhoun County, AR, Columbia County, AR, Hempstead County, AR, Lafayette County, AR, Little River County, AR, Miller County, AR, Nevada County, AR, Ouachita County, AR, Union County, AR, Bienville Parish, LA, Bossier Parish, LA, Caddo Parish, LA, Claiborne Parish, LA, De Soto Parish, LA, Lincoln Parish, LA, Red River Parish, LA, Sabine Parish, LA, Webster Parish, LA, Anderson County, TX, Angelina County, TX, Bowie County, TX, Camp County, TX, Cass County, TX, Cherokee County, TX, Freestone County, TX, Gregg County, TX, Harrison County, TX, Henderson County, TX, Houston County, TX, Leon County, TX, Limestone County, TX, Madison County, TX, Marion County, TX, Morris County, TX, Nacogdoches County, TX, Navarro County, TX, Panola County, TX, Polk County, TX, Rusk County, TX, Sabine County, TX, San Augustine County, TX, San Jacinto County, TX, Shelby County, TX, Smith County, TX, Titus County, TX, Trinity County, TX, Tyler County, TX, Upshur County, TX, Van Zandt County, TX, Walker County, TX, Wood County, TX
The radar
The Shreveport radar (KSHV), 115 km from the middle of the area, began a volume at 07:11 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 00:00Z, 7.1 hours before the alert went out and 124 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
- 543 m above ground
- 0-6 km bulk shear
- 54 kt
- 0-1 km storm-relative helicity
- 208 m²/s²
- 0-3 km storm-relative helicity
- 361 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
924
ACUS11 KWNS 150708
SWOMCD
SPC MCD 150708
ARZ000-LAZ000-TXZ000-OKZ000-151315-
Mesoscale Discussion 0084
NWS Storm Prediction Center Norman OK
0108 AM CST Mon Feb 15 2021
Areas affected...east-central and northeast TX...northwest
LA...southwest AR
Concerning...Heavy snow
Valid 150708Z - 151315Z
SUMMARY...Heavy snowfall rates around 1 inch per hour are expected
to develop from southwest to northeast across the Arklatex tonight.
Sleet is initially expected over parts of east TX northeast into
northwest LA. The changeover from sleet to moderate to heavy snow
will generally occur during the 3-5am CST period.
DISCUSSION...Water-vapor imagery shows a potent mid-level trough
over the southern High Plains progressing eastward towards the
Arklatex/northwest Gulf Coast. A plume of strong ascent/DCVA is
sweeping east across the TX Hill Country towards east TX/western LA
through early this morning. Radar mosaic as of 1am CST shows this
implied ascent manifest as a 150-mile-wide moderate to heavy snow
swath from south-central TX into northeast TX. Surface observations
upstream of the MCD area around Austin, TX are corroborating the
intensification of snowfall rates with heavy snow being reported at
several sites.
Model guidance is indicating an expanding heavy snowfall corridor
(rates 1 inch per hour, locally 1.5) as the large-scale, deep ascent
pivots east across east TX into LA tonight. The changeover from
sleet to heavy snow is expected to occur in northwest LA between
3-5am CST as temperatures decrease from +1 to 2 deg C to below
freezing in the 850-700 mb layer. A similar sleet-to-snow
transition in timing will occur for parts of east TX.
..Smith.. 02/15/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LZK...LCH...SHV...HGX...FWD...
LAT...LON 32199651 33959416 33839262 33069219 30539448 30359538
30709620 31509661 32199651SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Feb 15, 5:57 AM CST | Mesoscale Discussion | SPC | Arkansas, Ashley, Bradley, Chicot, Clay, Cleburne and 32 more | 6 hr |
| Feb 14, 10:53 PM CST | Mesoscale Discussion | SPC | Acadia, Allen, Avoyelles, Beauregard, Calcasieu, East Baton Rouge and 10 more | 4 hr |
| Feb 15, 3:09 AM CST | Mesoscale Discussion | SPC | Ascension, Assumption, East Baton Rouge, East Feliciana, Iberville, Livingston and 9 more | 6 hr |
| Feb 15, 9:28 AM CST | Mesoscale Discussion | SPC | Livingston, Saint Helena, Saint Tammany, Tangipahoa, Washington | 6 hr |
| Feb 14, 7:04 PM CST | Mesoscale Discussion | SPC | Bandera, Bastrop, Bell, Bexar, Blanco, Brazos and 35 more | 6 hr |
Nearby
Mesoscale Discussions in Texas, 2021Mesoscale Discussions in Arkansas, 2021Mesoscale Discussions in Louisiana, 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.