Alert archive / Oklahoma / Mesoscale Discussions in 2021
Mesoscale Discussion 458
The Storm Prediction Center issued this mesoscale discussion at Apr 28, 2021, 6:01 PM CDT for 9 counties in Arkansas; 13 counties in Oklahoma; Lamar County, Texas. It was in force for 119 min.
The area
The outline as issued.
The facts
- Issued
- Apr 28, 2021, 6:01 PM CDT (23:01 UTC)
- Expired
- Apr 28, 2021, 8:00 PM CDT
- In force
- 119 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
All 23 counties
Crawford County, AR, Franklin County, AR, Howard County, AR, Logan County, AR, Montgomery County, AR, Polk County, AR, Scott County, AR, Sebastian County, AR, Sevier County, AR, Atoka County, OK, Bryan County, OK, Choctaw County, OK, Coal County, OK, Haskell County, OK, Johnston County, OK, Latimer County, OK, LeFlore County, OK, Marshall County, OK, McCurtain County, OK, Pittsburg County, OK, Pushmataha County, OK, Sequoyah County, OK, Lamar County, TX
The radar
The Western Arkansas radar (KSRX), 119 km from the middle of the area, began a volume at 23:05 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, 11.0 hours before the alert went out and 265 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
- 678 J/kg
- Mixed-layer CIN
- -63 J/kg
- Mixed-layer LCL
- 635 m above ground
- 0-6 km bulk shear
- 51 kt
- 0-1 km storm-relative helicity
- 290 m²/s²
- 0-3 km storm-relative helicity
- 394 m²/s²
- Significant tornado parameter
- 1.7
- Supercell composite
- 12.5
The text
As transmitted.
928
ACUS11 KWNS 282301
SWOMCD
SPC MCD 282301
ARZ000-TXZ000-OKZ000-290100-
Mesoscale Discussion 0458
NWS Storm Prediction Center Norman OK
0601 PM CDT Wed Apr 28 2021
Areas affected...Southeast Oklahoma into Western Arkansas
Concerning...Severe potential...Watch possible
Valid 282301Z - 290100Z
Probability of Watch Issuance...40 percent
SUMMARY...An uptick in convection is noted across southeast Oklahoma
and may continue for the next few hours. A severe wind, and perhaps
a tornado, risk may evolve with these storms. Trends will be
monitored, and a watch is possible in the coming hours.
DISCUSSION...Recent IR imagery and lightning trends have shown a
notable intensification in convection within a warm frontal zone
over southeast OK. This is likely the result of increasing lift as a
subtle mid-level impulse propagates over the region. Although storms
may initially be elevated along the frontal zone, decreasing MLCIN
may allow storms to become rooted in the boundary-layer with time.
As this occurs, further storm intensification is possible as 200-300
m2s2 effective SRH helps organize and strengthen mesocyclones. This
may also support a tornado threat as storms move towards western AR
for the next 1-2 hours. However, recent RAP guidance suggests 0-3 km
hodographs may weaken after 01 UTC as the 850 mb jet shifts to the
east into central AR. Additionally, storm motions along the
initiating boundary will increase the probability for destructive
storm interactions and gradual upscale growth. Nonetheless, any
supercell that can become established within this regime will pose a
risk for at least marginally severe hail and damaging winds. Trends
will continue to be monitored, and a watch is possible if a more
robust severe/tornado threat becomes apparent.
..Moore/Guyer.. 04/28/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LZK...SHV...TSA...FWD...OUN...
LAT...LON 34109692 34549690 35159606 35569507 35809413 35379353
34889344 34249360 33789400 33659493 33659605 33769680
34109692SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 28, 3:01 AM CDT | Tornado Watch | SPC | Benton, Carroll, Crawford, Madison, Washington | 7 hr |
| Apr 28, 6:35 AM CDT | Mesoscale Discussion | SPC | Washington | 3 hr |
| Apr 28, 8:52 AM CDT | Mesoscale Discussion | SPC | Baxter, Boone, Clay, Cleburne, Conway, Craighead and 17 more | 113 min |
| Apr 28, 9:25 AM CDT | Mesoscale Discussion | SPC | Carroll, Crawford, Madison, Washington | 65 min |
| Apr 28, 10:56 AM CDT | Mesoscale Discussion | SPC | Fulton | 64 min |
| Apr 27, 8:01 PM CDT | Mesoscale Discussion | SPC | Comanche, Cotton, Jefferson, Stephens, Tillman | 89 min |
| Apr 27, 8:23 PM CDT | Severe Thunderstorm Watch | SPC | Carter, Cleveland, Comanche, Cotton, Garvin, Jefferson and 10 more | 7 hr |
| Apr 27, 10:39 PM CDT | Mesoscale Discussion | SPC | Andrews, Borden, Crane, Dawson, Ector, Howard and 5 more | 2 hr |
| Apr 28, 1:38 AM CDT | Mesoscale Discussion | SPC | Callahan, Coke, Coleman, Eastland, Glasscock, Jones and 10 more | 2 hr |
| Apr 28, 1:14 PM CDT | Mesoscale Discussion | SPC | Brown, Callahan, Coleman, Comanche, Cooke, Denton and 14 more | 2 hr |
| Apr 28, 1:57 PM CDT | Tornado Watch | SPC | Brown, Callahan, Coke, Coleman, Comanche, Concho and 16 more | 9 hr |
| Apr 28, 2:42 PM CDT | Mesoscale Discussion | SPC | Bandera, Blanco, Edwards, Gillespie, Kendall, Kerr and 9 more | 2 hr |
| Apr 28, 3:10 PM CDT | Tornado Watch | SPC | Atascosa, Bandera, Bexar, Blanco, Comal, Dimmit and 23 more | 8 hr |
| Apr 28, 3:40 PM CDT | Mesoscale Discussion | SPC | Brown, Callahan, Coleman, Comanche, Eastland, Runnels and 2 more | 95 min |
| Apr 28, 5:41 PM CDT | Mesoscale Discussion | SPC | Bandera, Bexar, Frio, Kendall, Kinney, Maverick and 4 more | 2 hr |
Nearby
Mesoscale Discussions in Oklahoma, 2021Mesoscale Discussions in Arkansas, 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.