Alert archive / Missouri / Mesoscale Discussions in 2021
Mesoscale Discussion 451
The Storm Prediction Center issued this mesoscale discussion at Apr 28, 2021, 12:33 PM CDT for 6 counties in Illinois; Ballard County, Carlisle County, McCracken County, Kentucky; 13 counties in Missouri. It was in force for 57 min.
The area
The outline as issued.
The facts
- Issued
- Apr 28, 2021, 12:33 PM CDT (17:33 UTC)
- Expired
- Apr 28, 2021, 1:30 PM CDT
- In force
- 57 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...severe thunderstorm watch likely
- Chance of a watch
- 80%
All 22 counties
Alexander County, IL, Johnson County, IL, Massac County, IL, Pulaski County, IL, Union County, IL, Williamson County, IL, Ballard County, KY, Carlisle County, KY, McCracken County, KY, Bollinger County, MO, Butler County, MO, Cape Girardeau County, MO, Carter County, MO, Madison County, MO, Mississippi County, MO, New Madrid County, MO, Perry County, MO, Reynolds County, MO, Ripley County, MO, Scott County, MO, Stoddard County, MO, Wayne County, MO
The radar
The Paducah radar (KPAH), 108 km from the middle of the area, began a volume at 17:32 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
Little Rock, AR (KLZK), launched 12:00Z, 5.6 hours before the alert went out and 245 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
- 845 J/kg
- Mixed-layer CIN
- -8 J/kg
- Mixed-layer LCL
- 593 m above ground
- 0-6 km bulk shear
- 48 kt
- 0-1 km storm-relative helicity
- 78 m²/s²
- 0-3 km storm-relative helicity
- 122 m²/s²
- Significant tornado parameter
- 0.4
- Supercell composite
- 1.7
The text
As transmitted.
987
ACUS11 KWNS 281733
SWOMCD
SPC MCD 281733
KYZ000-ILZ000-MOZ000-ARZ000-281830-
Mesoscale Discussion 0451
NWS Storm Prediction Center Norman OK
1233 PM CDT Wed Apr 28 2021
Areas affected...portions of southeast Missouri...far southwest
Illinois...extreme southwest Kentucky
Concerning...Severe potential...Severe Thunderstorm Watch likely
Valid 281733Z - 281830Z
Probability of Watch Issuance...80 percent
SUMMARY...The severe threat continues across Tornado Watch #0117,
and some threat for severe may persist downstream of the watch over
the next couple of hours. A couple of damaging gusts or a brief
tornado remain the primary threats. A Severe Thunderstorm Watch
issuance is likely shortly.
DISCUSSION...A QLCS persists roughly along a Texas/Shannon/Oregon
County line across southeast Missouri, with MRMS mosaic low-level
rotation track data showing modest circulations in progress. Ahead
of the QLCS, surface temperatures in the mid 70s, with near 70F
dewpoints, support around 1000 J/kg MLCAPE, evident via the latest
Mesoanalysis. While modest forcing and aforementioned instability
along a broad confluence/baroclinic zone is expected to support
downstream propagation of the QLCS, effective SRH has been gradually
weakening and is expected to continue waning over the next few
hours. While a brief tornado or two remain possible this afternoon,
damaging gusts are expected to remain the primary threat. As such, a
Severe Thunderstorm Watch issuance is likely shortly.
..Squitieri/Hart.. 04/28/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...PAH...MEG...LSX...LZK...SGF...
LAT...LON 36469119 37239119 37509088 37778994 37798903 37548860
37118850 36678905 36488962 36389073 36469119SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 28, 12:40 PM CDT | Severe Thunderstorm Watch | SPC | Alexander, Hardin, Johnson, Massac, Pope, Pulaski and 1 more | 7 hr |
| Apr 28, 3:29 PM CDT | Mesoscale Discussion | SPC | Alexander, Hardin, Johnson, Massac, Pope, Pulaski and 1 more | 91 min |
| Apr 28, 5:25 PM CDT | Mesoscale Discussion | SPC | Hardin, Massac, Pope | 2 hr |
| Apr 28, 8:52 AM CDT | Mesoscale Discussion | SPC | Butler, Dunklin, Howell, Oregon, Ozark, Ripley and 1 more | 113 min |
| Apr 28, 9:33 AM CDT | Tornado Watch | SPC | Christian, Douglas, Howell, Oregon, Ozark, Shannon and 4 more | 4 hr |
| Apr 28, 10:56 AM CDT | Mesoscale Discussion | SPC | Douglas, Howell, Oregon, Ozark, Shannon, Texas and 1 more | 64 min |
Nearby
Mesoscale Discussions in Missouri, 2021Mesoscale Discussions in Illinois, 2021Mesoscale Discussions in Kentucky, 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.