Alert archive / Illinois / Mesoscale Discussions in 2021
Mesoscale Discussion 347
The Storm Prediction Center issued this mesoscale discussion at Apr 9, 2021, 4:56 PM CDT for 4 states. It was in force for 64 min.
The area
The outline as issued.
The facts
- Issued
- Apr 9, 2021, 4:56 PM CDT (21:56 UTC)
- Expired
- Apr 9, 2021, 6:00 PM CDT
- In force
- 64 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
All 50 counties
Alexander County, IL, Clay County, IL, Edwards County, IL, Franklin County, IL, Gallatin County, IL, Hamilton County, IL, Hardin County, IL, Jackson County, IL, Jefferson County, IL, Johnson County, IL, Lawrence County, IL, Marion County, IL, Massac County, IL, Perry County, IL, Pope County, IL, Pulaski County, IL, Randolph County, IL, Richland County, IL, Saline County, IL, Union County, IL, Wabash County, IL, Washington County, IL, Wayne County, IL, White County, IL, Williamson County, IL, Gibson County, IN, Knox County, IN, Pike County, IN, Posey County, IN, Spencer County, IN, Vanderburgh County, IN, Warrick County, IN, Ballard County, KY, Crittenden County, KY, Daviess County, KY, Henderson County, KY, Livingston County, KY, McCracken County, KY, Union County, KY, Webster County, KY, Bollinger County, MO, Cape Girardeau County, MO, Carter County, MO, Madison County, MO, Perry County, MO, Saint Francois County, MO, Sainte Genevieve County, MO, Scott County, MO, Stoddard County, MO, Wayne County, MO
The radar
The Paducah radar (KPAH), 77 km from the middle of the area, began a volume at 21:59 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
Lincoln, IL (KILX), launched 12:00Z, 9.9 hours before the alert went out and 267 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
- 1 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 1099 m above ground
- 0-6 km bulk shear
- 43 kt
- 0-1 km storm-relative helicity
- 272 m²/s²
- 0-3 km storm-relative helicity
- 405 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
696
ACUS11 KWNS 092157
SWOMCD
SPC MCD 092156
KYZ000-INZ000-ILZ000-MOZ000-092300-
Mesoscale Discussion 0347
NWS Storm Prediction Center Norman OK
0456 PM CDT Fri Apr 09 2021
Areas affected...Portions of southeast Missouri...southern
Illinois...far southwest Indiana...far western Kentucky
Concerning...Severe potential...Watch unlikely
Valid 092156Z - 092300Z
Probability of Watch Issuance...20 percent
SUMMARY...Scattered thunderstorm development is underway, atop a dry
boundary layer. Some of the stronger storms may support large hail
development in addition to a few damaging gusts. After collaboration
with WFO PAH, a WW issuance is unlikely.
DISCUSSION...Semi-discrete convection has been gradually maturing
within a broad confluence zone, with MRMS mosaic radar data
depicting 1hr MESH approaching the 1 inch threshold. Surface
temperatures have exceeded 80F, with surface dewpoints barely
reaching 50 F. A dry boundary layer is in place, supporting
low-level lapse rates exceeding 9 C/km across much of the Ohio
Valley. With the latest Mesoanalysis sampling up to 7 C/km lapse
rates, up to 1000 J/kg MLCAPE, and 30-40 kts of effective bulk
shear, large hail may accompany some the strongest, longest lived
updrafts. The dry boundary layer may also support efficient downward
momentum transport of some of the stronger downdraft cores, though
it is unclear how widespread the more damaging winds will be given
tropospheric winds remaining generally below 35 kts beneath 500 mb.
..Squitieri.. 04/09/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LMK...IND...PAH...ILX...LSX...SGF...
LAT...LON 36899122 37859046 38398976 38798876 38918786 38868736
38608698 38098686 37618712 37288796 36928896 36818976
36739018 36899122SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 9, 2:50 PM CDT | Mesoscale Discussion | SPC | Barry, Butler, Carter, Christian, Dade, Douglas and 18 more | 85 min |
| Apr 9, 3:13 PM CDT | Severe Thunderstorm Watch | SPC | Barry, Christian, Douglas, Greene, Howell, Jasper and 11 more | 7 hr |
| Apr 9, 3:42 PM CDT | Severe Thunderstorm Watch | SPC | Dunklin, Pemiscot | 7 hr |
| Apr 9, 6:34 PM CDT | Mesoscale Discussion | SPC | Barry, Christian, Dade, Greene, Jasper, Lawrence and 3 more | 116 min |
Nearby
Mesoscale Discussions in Illinois, 2021Mesoscale Discussions in Missouri, 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.