Alert archive / Texas / Mesoscale Discussions in 2021

Mesoscale Discussion 139

February 28, 20218 counties in Arkansas; McCurtain County, Oklahoma; 14 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Feb 28, 2021, 5:28 PM CST for 8 counties in Arkansas; McCurtain County, Oklahoma; 14 counties in Texas. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Feb 28, 2021, 5:28 PM CST (23:28 UTC)
Expired: Feb 28, 2021, 7:30 PM CST
In force: 2 hr
Issued by: the Storm Prediction Center
Concerning: Severe thunderstorm watch 12

All 23 counties

Hempstead County, AR, Howard County, AR, Lafayette County, AR, Little River County, AR, Miller County, AR, Nevada County, AR, Pike County, AR, Sevier County, AR, McCurtain County, OK, Bowie County, TX, Camp County, TX, Cass County, TX, Delta County, TX, Franklin County, TX, Hopkins County, TX, Marion County, TX, Morris County, TX, Rains County, TX, Red River County, TX, Titus County, TX, Upshur County, TX, Van Zandt County, TX, Wood County, TX

The radar

The Shreveport radar (KSHV), 127 km from the middle of the area, began a volume at 23:30 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 14Feb 28, 5:50 PM CST

The nearest sounding before it

Shreveport, LA (KSHV), launched 12:00Z, 11.5 hours before the alert went out and 131 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 458 J/kg
Mixed-layer CIN: -126 J/kg
Mixed-layer LCL: 573 m above ground
0-6 km bulk shear: 53 kt
0-1 km storm-relative helicity: 321 m²/s²
0-3 km storm-relative helicity: 414 m²/s²
Significant tornado parameter: 0.4
Supercell composite: 1.2

Open this sounding in Storm Lab

The text

As transmitted.

080 
ACUS11 KWNS 282329
SWOMCD
SPC MCD 282328 
ARZ000-LAZ000-TXZ000-OKZ000-010130-

Mesoscale Discussion 0139
NWS Storm Prediction Center Norman OK
0528 PM CST Sun Feb 28 2021

Areas affected...Arklatex

Concerning...Severe Thunderstorm Watch 12...

Valid 282328Z - 010130Z

The severe weather threat for Severe Thunderstorm Watch 12
continues.

SUMMARY...An isolated severe threat is expected to continue for
several more hours across parts of the Arklatex this evening.
Coordination with weather forecast offices will take place prior to
the expiration of watch 12. The result may be reissuance further
east or extension in time.

DISCUSSION...The latest water vapor imagery shows a plume of
mid-level moisture extending east-northeastward across the southern
Plains into the Arklatex. Thunderstorms are ongoing within that
plume from northeast Texas extending northeastward across Arkansas.
The storms are located along and just ahead of a slow-moving cold
front. A southwest-to-northeast gradient of instability is evident
to the southeast of the front with the RAP estimating MLCAPE in the
500 to 1500 J/kg range. Continued thunderstorm development is
expected over the Arklatex for several more hours as large-scale
ascent and warm advection provide support. In addition to the
instability, the Shreveport WSR-88D VWP has 0-6 km shear near 60 Kt
suggesting that an isolated severe threat will continue. Hail and
marginally severe wind gusts will be possible although the threat
should remain isolated.

..Broyles/Grams.. 02/28/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...LZK...SHV...TSA...FWD...

LAT...LON   32339542 32359603 32859602 32869597 32989589 33499581
            33499555 33449544 33409532 33939528 34029515 34229511
            34459502 34519461 34479441 34209448 34199422 34389421
            34319348 34049342 33889334 33799309 33529306 33479340
            33049349 33069400 32759403 32709405 32679429 32679443
            32779462 32649472 32559514 32599541 32689564 32469555
            32389551 32339542

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Feb 28, 9:59 AM CST	Mesoscale Discussion	SPC	Howard, Polk, Sevier	91 min
Feb 28, 10:43 AM CST	Severe Thunderstorm Watch	SPC	Hempstead, Howard, Lafayette, Little River, Miller, Montgomery and 5 more	7 hr
Feb 28, 1:01 PM CST	Mesoscale Discussion	SPC	Arkansas, Clark, Clay, Cleburne, Cleveland, Conway and 32 more	119 min
Feb 28, 2:22 PM CST	Tornado Watch	SPC	Arkansas, Bradley, Calhoun, Clark, Clay, Cleburne and 32 more	8 hr
Feb 28, 2:25 PM CST	Mesoscale Discussion	SPC	Hempstead, Howard, Little River, Miller, Pike, Sevier	2 hr
Feb 28, 4:40 PM CST	Mesoscale Discussion	SPC	Arkansas, Bradley, Calhoun, Clark, Cleveland, Craighead and 23 more	95 min
Feb 28, 5:54 PM CST	Severe Thunderstorm Watch	SPC	Columbia, Hempstead, Lafayette, Miller, Nevada, Union	4 hr
Feb 28, 1:47 AM CST	Mesoscale Discussion	SPC	Cleveland, Creek, Lincoln, Mayes, Okfuskee, Oklahoma and 8 more	2 hr

Nearby

Mesoscale Discussions in Texas, 2021 Mesoscale Discussions in Arkansas, 2021 Mesoscale Discussions in Oklahoma, 2021 Every 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.