Alert archive / Illinois / Mesoscale Discussions in 2021
Mesoscale Discussion 1109
The Storm Prediction Center issued this mesoscale discussion at Jun 26, 2021, 11:45 AM CDT for 27 counties in Illinois; Jasper County, Lake County, Newton County, Indiana; 5 counties in Missouri. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Jun 26, 2021, 11:45 AM CDT (16:45 UTC)
- Expired
- Jun 26, 2021, 1:45 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 60%
All 35 counties
Calhoun County, IL, Cass County, IL, Champaign County, IL, Christian County, IL, DeWitt County, IL, Ford County, IL, Greene County, IL, Grundy County, IL, Iroquois County, IL, Jersey County, IL, Kankakee County, IL, Livingston County, IL, Logan County, IL, Macon County, IL, Macoupin County, IL, Madison County, IL, Mason County, IL, McLean County, IL, Menard County, IL, Montgomery County, IL, Morgan County, IL, Piatt County, IL, Sangamon County, IL, Scott County, IL, Tazewell County, IL, Will County, IL, Woodford County, IL, Jasper County, IN, Lake County, IN, Newton County, IN, City of Saint Louis, MO, Lincoln County, MO, Saint Charles County, MO, Saint Louis County, MO, Warren County, MO
The radar
The Lincoln radar (KILX), 46 km from the middle of the area, began a volume at 16:45 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
Lincoln, IL (KILX), launched 12:00Z, 4.8 hours before the alert went out and 93 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
- 683 J/kg
- Mixed-layer CIN
- -28 J/kg
- Mixed-layer LCL
- 684 m above ground
- 0-6 km bulk shear
- 31 kt
- 0-1 km storm-relative helicity
- 263 m²/s²
- 0-3 km storm-relative helicity
- 229 m²/s²
- Significant tornado parameter
- 0.5
- Supercell composite
- 3.1
The text
As transmitted.
396
ACUS11 KWNS 261645
SWOMCD
SPC MCD 261645
INZ000-ILZ000-MOZ000-261845-
Mesoscale Discussion 1109
NWS Storm Prediction Center Norman OK
1145 AM CDT Sat Jun 26 2021
Areas affected...Parts of east central Missouri through
central/northeastern Illinois and adjacent northwestern Indiana
Concerning...Severe potential...Watch possible
Valid 261645Z - 261845Z
Probability of Watch Issuance...60 percent
SUMMARY...Thunderstorm development likely will continue to increase
through 1-3 PM CDT, posing at least some risk for isolated tornadoes
and damaging downbursts.
DISCUSSION...Deepening convective development is ongoing along a
narrow corridor of destabilization largely driven by daytime
heating. This is occurring near a remnant convectively generated
surface boundary, along which low-level convergence is focused and
maintaining mid 70s F surface dew points, from the Greater St. Louis
metro area north-northeastward into the Greater Chicago area. This
is also along the southeastern periphery of a lower/mid tropospheric
cyclone centered over Iowa, with a remnant MCV also migrating
northeast of the Springfield, MO area, toward St. Louis.
Lapse rates are generally weak, but the low-level moisture appears
to be contributing to mixed-layer CAPE in excess of 1000 J/kg, which
could increase to 1500-2000 J/kg with continuing insolation.
Furthermore, the axis of destabilization is aligned with a
south-southwesterly 850 mb jet migrating across the middle
Mississippi Valley toward the Great Lakes region.
Moderate to strong low-level shear will support rotation in
developing updrafts, some of which may occasionally strengthen and
pose a risk for at least brief tornadoes. Otherwise, consolidating/
upscale growing storm clusters are also possible and may be
accompanied by a risk for damaging downbursts.
..Kerr/Hart.. 06/26/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LOT...ILX...LSX...
LAT...LON 39299087 40229010 41468835 41748733 41088693 39378923
38439013 38339081 38649123 39299087SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 25, 7:05 PM CDT | Mesoscale Discussion | SPC | Iroquois, Kankakee, Vermilion | 55 min |
| Jun 25, 8:34 PM CDT | Mesoscale Discussion | SPC | Adams, Brown, Calhoun, Cass, Champaign, Christian and 30 more | 86 min |
| Jun 25, 10:31 PM CDT | Mesoscale Discussion | SPC | Bond, Calhoun, Cass, Champaign, Christian, Coles and 30 more | 59 min |
| Jun 26, 12:05 PM CDT | Tornado Watch | SPC | Cass, Champaign, Christian, Coles, Cook, Cumberland and 24 more | 9 hr |
| Jun 26, 2:47 PM CDT | Mesoscale Discussion | SPC | Calhoun, DeWitt, Ford, Greene, Iroquois, Jersey and 8 more | 118 min |
| Jun 26, 6:08 PM CDT | Mesoscale Discussion | SPC | Champaign, Coles, Cumberland, Douglas, Edgar, Ford and 5 more | 67 min |
| Jun 26, 12:48 PM CDT | Mesoscale Discussion | SPC | LaPorte, Saint Joseph | 57 min |
| Jun 26, 6:47 PM CDT | Severe Thunderstorm Watch | SPC | Carroll, Clinton, Fountain, Montgomery, Parke, Tippecanoe and 2 more | 3 hr |
Nearby
Mesoscale Discussions in Illinois, 2021Mesoscale Discussions in Missouri, 2021Mesoscale Discussions in Indiana, 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.