Alert archive / Texas / Mesoscale Discussions in 2021
Mesoscale Discussion 415
The Storm Prediction Center issued this mesoscale discussion at Apr 23, 2021, 11:19 PM CDT for Howard County, Sevier County, Arkansas; Choctaw County, McCurtain County, Pushmataha County, Oklahoma; 8 counties in Texas. It was in force for 116 min.
The area
The outline as issued.
The facts
- Issued
- Apr 23, 2021, 11:19 PM CDT (04:19 UTC)
- Expired
- Apr 24, 2021, 1:15 AM CDT
- In force
- 116 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 103
Counties Howard County, AR, Sevier County, AR, Choctaw County, OK, McCurtain County, OK, Pushmataha County, OK, Camp County, TX, Delta County, TX, Fannin County, TX, Franklin County, TX, Hopkins County, TX, Lamar County, TX, Red River County, TX, Titus County, TX
The radar
The Western Arkansas radar (KSRX), 200 km from the middle of the area, began a volume at 04:20 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
Fort Worth, TX (KFWD), launched 00:00Z, 4.3 hours before the alert went out and 188 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
- 364 J/kg
- Mixed-layer CIN
- -58 J/kg
- Mixed-layer LCL
- 812 m above ground
- 0-6 km bulk shear
- 47 kt
- 0-1 km storm-relative helicity
- 252 m²/s²
- 0-3 km storm-relative helicity
- 291 m²/s²
- Significant tornado parameter
- 0.6
- Supercell composite
- 7.5
The text
As transmitted.
316
ACUS11 KWNS 240419
SWOMCD
SPC MCD 240419
ARZ000-TXZ000-OKZ000-240615-
Mesoscale Discussion 0415
NWS Storm Prediction Center Norman OK
1119 PM CDT Fri Apr 23 2021
Areas affected...Parts of southeastern Oklahoma...northeast
Texas...southwestern Arkansas
Concerning...Severe Thunderstorm Watch 103...
Valid 240419Z - 240615Z
The severe weather threat for Severe Thunderstorm Watch 103
continues.
SUMMARY...Although substantive further intensification appears
unlikely, an organized cluster of thunderstorms may be accompanied
by strong surface gusts occasionally approaching severe limits as it
continues across the Red River Valley vicinity, toward the
Ark-La-Tex region, through Midnight-2 AM CDT. Given the generally
marginal nature of the continuing severe risk, a new severe weather
watch is not anticipated, but trends will continue to be monitored.
DISCUSSION...An organized cluster of thunderstorms continues to
propagate east-southeastward around 30 kt, across the Red River
Valley vicinity. This appears focused along the leading edge of
stronger cooling aloft (associated with the mid-level cold core of
the vigorous short wave trough progressing east of the southern
Rockies), supported by warm advection along a remnant frontal zone
associated stronger daytime differential surface heating and
boundary-layer mixing. While this frontal zone becomes gradually
weaker with east-southeastward extent, inflow of moist air with
moderately large CAPE in excess of 1000 J/kg may maintain this
activity into the 05-07Z time frame.
Although activity appears generally rooted above a relatively cool
near-surface layer stable layer, and is embedded within a rather
modest deep-layer westerly flow regime, shear within the convective
layer appears strong. And a 30-50+ kt rear inflow jet appears to
have developed, with a few strong surface gusts approaching severe
limits occasionally reaching the surface, based on Oklahoma mesonet
observations.
..Kerr.. 04/24/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LZK...SHV...TSA...FWD...OUN...
LAT...LON 34099593 34859571 34079395 32759509 33489676 33689645
34099593SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 23, 7:43 PM CDT | Mesoscale Discussion | SPC | Carter, Comanche, Cotton, Garvin, Greer, Harmon and 10 more | 2 hr |
| Apr 23, 8:02 PM CDT | Severe Thunderstorm Watch | SPC | Bryan, Carter, Cotton, Jefferson, Johnston, Love and 3 more | 4 hr |
| 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 Texas, 2021Mesoscale Discussions in Oklahoma, 2021Mesoscale Discussions in Arkansas, 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.