Alert archive / Oklahoma / Mesoscale Discussions in 2021
Mesoscale Discussion 413
The Storm Prediction Center issued this mesoscale discussion at Apr 23, 2021, 7:43 PM CDT for 16 counties in Oklahoma; 7 counties in Texas. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Apr 23, 2021, 7:43 PM CDT (00:43 UTC)
- Expired
- Apr 23, 2021, 9:45 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 100
All 23 counties
Carter County, OK, Comanche County, OK, Cotton County, OK, Garvin County, OK, Greer County, OK, Harmon County, OK, Jackson County, OK, Jefferson County, OK, Johnston County, OK, Kiowa County, OK, Love County, OK, Marshall County, OK, Murray County, OK, Pontotoc County, OK, Stephens County, OK, Tillman County, OK, Clay County, TX, Cooke County, TX, Grayson County, TX, Hardeman County, TX, Montague County, TX, Wichita County, TX, Wilbarger County, TX
The radar
The Altus AFB radar (KFDR), 39 km from the middle of the area, began a volume at 00:46 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
Norman, OK (KOUN), launched 00:00Z, 0.7 hours before the alert went out and 150 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
- 486 J/kg
- Mixed-layer CIN
- -47 J/kg
- Mixed-layer LCL
- 504 m above ground
- 0-6 km bulk shear
- 59 kt
- 0-1 km storm-relative helicity
- 345 m²/s²
- 0-3 km storm-relative helicity
- 408 m²/s²
- Significant tornado parameter
- 1.2
- Supercell composite
- 6.8
The text
As transmitted.
162
ACUS11 KWNS 240044
SWOMCD
SPC MCD 240043
OKZ000-TXZ000-240245-
Mesoscale Discussion 0413
NWS Storm Prediction Center Norman OK
0743 PM CDT Fri Apr 23 2021
Areas affected...Northwest Texas and Southwest Oklahoma
Concerning...Tornado Watch 100...
Valid 240043Z - 240245Z
The severe weather threat for Tornado Watch 100 continues.
SUMMARY...The tornado threat will continue to diminish over the next
hour, but a wind/hail threat will likely persist into the late
evening hours. A new watch may be needed to address this potential.
DISCUSSION...The notable supercell with a history of producing
tornadoes and large hail along the Red River Valley has become
outflow dominant over the past 30 minutes and is growing upscale
within a cluster of new convective development. Despite this, the
evolving cluster continues to show a strong presentation in IR
imagery and resides within a favorable environment featuring
1500-2000 J/kg MLCAPE and 40 knots of effective bulk shear. This
should continue to support a hail and damaging wind potential for
the next 1-2 hours. Given that these storms remain along/just north
of a weak warm frontal zone where 0-1 km shear is maximized (per
recent KFDR VWP observations), a brief tornado or two will remain
possible in the near term. Continued upscale growth, along with a
gradual increase in surface-based inhibition and weakening low-level
shear in the vicinity of the surface low, should continue to reduce
the tornado potential heading into the late evening hours and favor
a wind/hail threat. A similar evolution is anticipated for a second
developing cluster of storms further upstream along the OK/TX
Panhandle border. A new watch, or a watch extension, may be
considered to address the wind/hail threat by 01 UTC.
..Moore.. 04/24/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FWD...OUN...LUB...AMA...
LAT...LON 34959997 34989929 34879856 34789778 34729657 34149620
33409652 33409774 33559838 33719908 33909968 34110006
34330019 34959997SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 23, 8:02 PM CDT | Severe Thunderstorm Watch | SPC | Bryan, Carter, Cotton, Jefferson, Johnston, Love and 3 more | 4 hr |
| Apr 23, 11:19 PM CDT | Mesoscale Discussion | SPC | Choctaw, McCurtain, Pushmataha | 116 min |
| Apr 23, 7:05 PM CDT | Severe Thunderstorm Watch | SPC | Atascosa, Bexar, DeWitt, Fayette, Gonzales, Guadalupe and 3 more | 3 hr |
| Apr 23, 7:42 PM CDT | Severe Thunderstorm Watch | SPC | Bee, Goliad, Live Oak, Victoria | 2 hr |
Nearby
Mesoscale Discussions in Oklahoma, 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.