Alert archive / Illinois / Mesoscale Discussions in 2021
Mesoscale Discussion 1383
The Storm Prediction Center issued this mesoscale discussion at Jul 29, 2021, 12:32 AM CDT for 17 counties in Illinois; 13 counties in Indiana; 6 counties in Michigan. It was in force for 88 min.
The area
The outline as issued.
The facts
- Issued
- Jul 29, 2021, 12:32 AM CDT (05:32 UTC)
- Expired
- Jul 29, 2021, 2:00 AM CDT
- In force
- 88 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...severe thunderstorm watch likely
- Chance of a watch
- 80%
All 36 counties
Boone County, IL, Carroll County, IL, Cook County, IL, DeKalb County, IL, DuPage County, IL, Grundy County, IL, Jo Daviess County, IL, Kane County, IL, Kankakee County, IL, Kendall County, IL, Lake County, IL, Lee County, IL, McHenry County, IL, Ogle County, IL, Stephenson County, IL, Will County, IL, Winnebago County, IL, Elkhart County, IN, Fulton County, IN, Jasper County, IN, Kosciusko County, IN, LaGrange County, IN, Lake County, IN, LaPorte County, IN, Marshall County, IN, Newton County, IN, Porter County, IN, Pulaski County, IN, Saint Joseph County, IN, Starke County, IN, Allegan County, MI, Berrien County, MI, Cass County, MI, Kalamazoo County, MI, Saint Joseph County, MI, Van Buren County, MI
The radar
The Chicago radar (KLOT), 61 km from the middle of the area, began a volume at 05:32 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
Lincoln, IL (KILX), launched 00:00Z, 5.5 hours before the alert went out and 208 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
- 332 J/kg
- Mixed-layer CIN
- -288 J/kg
- Mixed-layer LCL
- 1661 m above ground
- 0-6 km bulk shear
- 39 kt
- 0-1 km storm-relative helicity
- 57 m²/s²
- 0-3 km storm-relative helicity
- 101 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.1
The text
As transmitted.
508
ACUS11 KWNS 290532
SWOMCD
SPC MCD 290532
INZ000-MIZ000-ILZ000-290700-
Mesoscale Discussion 1383
NWS Storm Prediction Center Norman OK
1232 AM CDT Thu Jul 29 2021
Areas affected...Portions of northern IL/IN and southwestern Lower
MI
Concerning...Severe potential...Severe Thunderstorm Watch likely
Valid 290532Z - 290700Z
Probability of Watch Issuance...80 percent
SUMMARY...A threat for at least scattered damaging wind gusts should
continue overnight. Severe Thunderstorm Watch issuance is likely
soon.
DISCUSSION...A well-organized MCS is ongoing as of 0530Z across much
of southern WI. The eastern segment of this MCS is moving
south-southeastward around 35-45 kt, and multiple reports of damage
have recently occurred in eastern WI. With its current motion,
expectations are for this MCS to continue into parts of northern
IL/IN and perhaps southwestern Lower MI in the next couple of hours.
Although some convective inhibition is present owing to slight
nocturnal cooling of the boundary layer, the 00Z sounding from DVN
did show ample instability with a very moist low-level airmass
remaining over this region. Given the linear nature of the ongoing
storms, the presence of at least moderate instability downstream,
and 35-45 kt of deep-layer shear, at least scattered damaging winds
should continue to be a threat for several more hours. Accordingly,
a downstream Severe Thunderstorm Watch will likely be issued soon to
address this threat.
..Gleason/Edwards.. 07/29/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...IWX...GRR...LOT...DVN...
LAT...LON 42449045 41758949 41038827 40828715 40848620 41118554
41818532 42338533 42618615 42428697 42449045SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 29, 1:00 AM CDT | Severe Thunderstorm Watch | SPC | Boone, Bureau, Carroll, Cook, DeKalb, DuPage and 18 more | 5 hr |
| Jul 29, 1:34 AM CDT | Mesoscale Discussion | SPC | Boone, Cook, DeKalb, DuPage, Kane, Kendall and 3 more | 86 min |
| Jul 29, 3:18 AM CDT | Mesoscale Discussion | SPC | Cook, DeKalb, DuPage, Grundy, Iroquois, Kankakee and 4 more | 87 min |
| Jul 29, 2:19 PM CDT | Mesoscale Discussion | SPC | Adams, Brown, Cass, Champaign, Christian, Clark and 34 more | 116 min |
| Jul 29, 4:55 AM CDT | Mesoscale Discussion | SPC | Adams, Allen, Blackford, DeKalb, Grant, Huntington and 6 more | 95 min |
| Jul 29, 2:13 PM CDT | Severe Thunderstorm Watch | SPC | Dearborn, Fayette, Franklin, Ohio, Ripley, Switzerland and 2 more | 7 hr |
| Jul 29, 5:34 PM CDT | Mesoscale Discussion | SPC | Dearborn, Fayette, Franklin, Henry, Rush, Union and 1 more | 116 min |
Nearby
Mesoscale Discussions in Illinois, 2021Mesoscale Discussions in Indiana, 2021Mesoscale Discussions in Michigan, 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.