Alert archive / Texas / Mesoscale Discussions in 2021
Mesoscale Discussion 135
The Storm Prediction Center issued this mesoscale discussion at Feb 28, 2021, 9:59 AM CST for Howard County, Polk County, Sevier County, Arkansas; Choctaw County, McCurtain County, Pushmataha County, Oklahoma; 18 counties in Texas. It was in force for 91 min.
The area
The outline as issued.
The facts
- Issued
- Feb 28, 2021, 9:59 AM CST (15:59 UTC)
- Expired
- Feb 28, 2021, 11:30 AM CST
- In force
- 91 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch likely
- Chance of a watch
- 80%
All 24 counties
Howard County, AR, Polk County, AR, Sevier County, AR, Choctaw County, OK, McCurtain County, OK, Pushmataha County, OK, Bosque County, TX, Collin County, TX, Dallas County, TX, Delta County, TX, Ellis County, TX, Fannin County, TX, Franklin County, TX, Hill County, TX, Hopkins County, TX, Hunt County, TX, Johnson County, TX, Kaufman County, TX, Lamar County, TX, Rains County, TX, Red River County, TX, Rockwall County, TX, Somervell County, TX, Tarrant County, TX
The radar
The Dallas/Ft Worth radar (KFWS), 95 km from the middle of the area, began a volume at 16:00 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.
The nearest sounding before it
Fort Worth, TX (KFWD), launched 12:00Z, 4.0 hours before the alert went out and 80 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
- 1316 J/kg
- Mixed-layer CIN
- -80 J/kg
- Mixed-layer LCL
- 666 m above ground
- 0-6 km bulk shear
- 71 kt
- 0-1 km storm-relative helicity
- 165 m²/s²
- 0-3 km storm-relative helicity
- 109 m²/s²
- Significant tornado parameter
- 1.2
- Supercell composite
- 3.6
The text
As transmitted.
752
ACUS11 KWNS 281559
SWOMCD
SPC MCD 281559
ARZ000-TXZ000-OKZ000-281730-
Mesoscale Discussion 0135
NWS Storm Prediction Center Norman OK
0959 AM CST Sun Feb 28 2021
Areas affected...northeast Texas through southeast Oklahoma and
southwest Arkansas
Concerning...Severe potential...Watch likely
Valid 281559Z - 281730Z
Probability of Watch Issuance...80 percent
SUMMARY...Thunderstorms are expected to increase in coverage and
intensity by late morning into the afternoon. Primary threats will
be isolated large hail and damaging wind gusts, though a tornado or
two will also be possible. A WW will likely be needed before 17Z.
DISCUSSION...As of mid morning a cold front extends from eastern OK
through north central and west central TX. An isolated thunderstorm
with mid-level updraft rotation has developed on the front and is
located just east of Gainesville with another isolated storm near
Mineral Wells. The downstream warm sector is already moderately
unstable with 1000-1500 J/kg MLCAPE supported by upper 60s F
dewpoints and 7-7.5 C/km mid-level lapse rates. Further
destabilization will occur, but will be limited to some degree by
widespread multi-layer clouds. Weak, progressive impulses embedded
within the southwesterly upper flow regime and forcing along the
cold front will contribute to an increase in thunderstorm coverage
later this morning as the boundary layer slowly warms. The primary
low-level jet has shifted east of this region resulting in small 0-1
km hodographs. However, a belt of strong southwesterly winds
increasing to around 70 kt at 500 mb resides above the warm sector
and is contributing to 60+ kt effective bulk shear. Therefore, some
storms should organize with supercells and bowing segments likely,
eventually consolidating into a dominant linear mode. Large hail and
isolated damaging wind will be the main threats. The small low-level
hodographs should tend to limit overall tornado threat. However, a
tornado or two cannot be ruled out.
..Dial/Hart.. 02/28/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LZK...SHV...TSA...FWD...OUN...
LAT...LON 32559772 33599665 34899484 34329358 31909679 31859817
32559772SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| 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, 5:28 PM CST | Mesoscale Discussion | SPC | Hempstead, Howard, Lafayette, Little River, Miller, Nevada and 2 more | 2 hr |
| 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, 2021Mesoscale Discussions in Arkansas, 2021Mesoscale Discussions in Oklahoma, 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.