Alert archive / Illinois / Mesoscale Discussions in 2021
Mesoscale Discussion 1470
The Storm Prediction Center issued this mesoscale discussion at Aug 11, 2021, 1:20 AM CDT for 21 counties in Illinois; 5 counties in Indiana. It was in force for 115 min.
The area
The outline as issued.
The facts
- Issued
- Aug 11, 2021, 1:20 AM CDT (06:20 UTC)
- Expired
- Aug 11, 2021, 3:15 AM CDT
- In force
- 115 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
All 26 counties
Bureau County, IL, Ford County, IL, Fulton County, IL, Grundy County, IL, Henry County, IL, Iroquois County, IL, Kankakee County, IL, Kendall County, IL, Knox County, IL, LaSalle County, IL, Livingston County, IL, Marshall County, IL, McLean County, IL, Peoria County, IL, Putnam County, IL, Stark County, IL, Tazewell County, IL, Vermilion County, IL, Warren County, IL, Will County, IL, Woodford County, IL, Benton County, IN, Jasper County, IN, Lake County, IN, Newton County, IN, Warren County, IN
The radar
The Lincoln radar (KILX), 91 km from the middle of the area, began a volume at 06:23 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 00:00Z, 6.3 hours before the alert went out and 82 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
- 2608 J/kg
- Mixed-layer CIN
- -33 J/kg
- Mixed-layer LCL
- 1127 m above ground
- 0-6 km bulk shear
- 16 kt
- 0-1 km storm-relative helicity
- 167 m²/s²
- 0-3 km storm-relative helicity
- 194 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
758
ACUS11 KWNS 110620
SWOMCD
SPC MCD 110620
INZ000-ILZ000-110815-
Mesoscale Discussion 1470
NWS Storm Prediction Center Norman OK
0120 AM CDT Wed Aug 11 2021
Areas affected...North-Central/Central IL...Far Northwest IN
Concerning...Severe potential...Watch possible
Valid 110620Z - 110815Z
Probability of Watch Issuance...40 percent
SUMMARY...Thunderstorm development anticipated across
north-central/central IL and far northwest IN tonight. Some stronger
storms are possible and convective trends will be monitored for
potential watch issuance.
DISCUSSION...Recent IR satellite imagery shows some colder cloud
tops beginning to emerge along northern edge of low to mid-level
warm-air advection fostered by the low-level jet emanating out of
the southern Plains. This low-level jet is expected to spread
eastward/northeastward over the next few hours as an low-amplitude
shortwave trough moves out of the central Plains into IA and
southern MN. As it does, the continued warm-air advection will
likely result in convective initiation across central IL. Steep
mid-level lapse rates remain in place, fostering the potential for
strong buoyancy as the high theta-e air along the MS River is
advected northeastward. Effective bulk shear across the region also
remains strong enough for organization/rotation within any stronger,
more persistent updrafts. Even so, overall convective evolution
remains uncertain, particularly across northeast IL and adjacent
northwest IN where the low-level air mass has been stabilized by
earlier storms.
Given the anticipated elevated character of the storms, large hail
appears to be the main severe threat. A strong cold pool could
theoretically penetrate the low-level stability and produce gusts at
the surface, but the development of such a cold pool would be
dependent on organization into a convective line, which is uncertain
at this time. Overall trends will be monitored closely for enough
storm strength and coverage to merit a watch.
..Mosier/Guyer.. 08/11/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...IWX...IND...LOT...ILX...DVN...
LAT...LON 40378995 40569106 41469047 41758968 41628793 41518739
41188695 40338704 40138760 40308904 40378995SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 10, 7:38 PM CDT | Severe Thunderstorm Watch | SPC | Kankakee | 5 hr |
| Aug 11, 4:49 AM CDT | Mesoscale Discussion | SPC | Adams | 86 min |
| Aug 11, 6:26 AM CDT | Mesoscale Discussion | SPC | Adams, Brown, Cass, Fulton, Hancock, Henderson and 12 more | 2 hr |
| Aug 11, 8:34 AM CDT | Mesoscale Discussion | SPC | Bureau, Cook, DeKalb, DuPage, Ford, Grundy and 13 more | 86 min |
| Aug 11, 8:52 AM CDT | Severe Thunderstorm Watch | SPC | Cook, DeKalb, DuPage, Grundy, Kane, Kankakee and 6 more | 4 hr |
| Aug 11, 9:52 AM CDT | Mesoscale Discussion | SPC | Cook, DuPage, Grundy, Kane, Kankakee, Lake and 1 more | 83 min |
| Aug 11, 3:56 PM CDT | Mesoscale Discussion | SPC | Carroll, Hancock, Henderson, Henry, Jo Daviess, Mercer and 2 more | 3 hr |
| Aug 11, 5:40 PM CDT | Mesoscale Discussion | SPC | Carroll, Jo Daviess, Stephenson | 95 min |
| Aug 10, 7:12 PM CDT | Mesoscale Discussion | SPC | DeKalb, Elkhart, Kosciusko, LaGrange, Lake, LaPorte and 6 more | 63 min |
| Aug 10, 9:57 PM CDT | Mesoscale Discussion | SPC | Allen, DeKalb, Elkhart, Fulton, Huntington, Jasper and 8 more | 93 min |
| Aug 11, 10:50 AM CDT | Severe Thunderstorm Watch | SPC | Adams, Allen, Blackford, Cass, DeKalb, Elkhart and 18 more | 4 hr |
| Aug 11, 12:26 PM CDT | Mesoscale Discussion | SPC | Adams, Allen, DeKalb, Elkhart, Huntington, Kosciusko and 7 more | 94 min |
Nearby
Mesoscale Discussions in Illinois, 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.