Alert archive / Illinois / Mesoscale Discussions in 2021
Mesoscale Discussion 1475
The Storm Prediction Center issued this mesoscale discussion at Aug 11, 2021, 8:34 AM CDT for 19 counties in Illinois; 5 counties in Indiana. It was in force for 86 min.
The area
The outline as issued.
The facts
- Issued
- Aug 11, 2021, 8:34 AM CDT (13:34 UTC)
- Expired
- Aug 11, 2021, 10:00 AM CDT
- In force
- 86 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 60%
All 24 counties
Bureau County, IL, Cook County, IL, DeKalb County, IL, DuPage County, IL, Ford County, IL, Grundy County, IL, Iroquois County, IL, Kane County, IL, Kankakee County, IL, Kendall County, IL, LaSalle County, IL, Lee County, IL, Livingston County, IL, Marshall County, IL, Ogle County, IL, Putnam County, IL, Stark County, IL, Will County, IL, Woodford County, IL, Benton County, IN, Jasper County, IN, Lake County, IN, Newton County, IN, Porter County, IN
The radar
The Chicago radar (KLOT), 46 km from the middle of the area, began a volume at 13:34 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, 1.6 hours before the alert went out and 128 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
- 1930 J/kg
- Mixed-layer CIN
- -174 J/kg
- Mixed-layer LCL
- 1253 m above ground
- 0-6 km bulk shear
- 28 kt
- 0-1 km storm-relative helicity
- 228 m²/s²
- 0-3 km storm-relative helicity
- 185 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 4.4
The text
As transmitted.
710
ACUS11 KWNS 111334
SWOMCD
SPC MCD 111334
INZ000-ILZ000-111500-
Mesoscale Discussion 1475
NWS Storm Prediction Center Norman OK
0834 AM CDT Wed Aug 11 2021
Areas affected...Portions of northern IL and northwestern IN
Concerning...Severe potential...Watch possible
Valid 111334Z - 111500Z
Probability of Watch Issuance...60 percent
SUMMARY...Severe storms capable of producing both damaging winds and
large hail may continue this morning. Watch issuance is possible.
DISCUSSION...The northern segment of a small cluster of storms has
recently intensified across northern IL. The 12Z sounding from DVN
showed strengthening westerly flow in the 0-6 km layer, and these
storms may maintain their organization this morning as they move
eastward given the presence of 30-35 kt of deep-layer shear. This
convection is showing enhanced outbound velocities from KDVN at low
levels, and there is some concern for a scattered damaging wind
threat across northern IL, as 2000-2500 J/kg of MLCAPE is present
ahead of this activity. If current convective intensities are
maintained, then a watch may need to be considered downstream soon.
..Gleason/Thompson.. 08/11/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LOT...ILX...DVN...
LAT...LON 40538830 40908964 41299008 42038979 42178826 42058756
41578703 40608715 40538830SPC 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, 1:20 AM CDT | Mesoscale Discussion | SPC | Bureau, Ford, Fulton, Grundy, Henry, Iroquois and 15 more | 115 min |
| 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, 8:52 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.