Alert archive / Indiana / Mesoscale Discussions in 2021
Mesoscale Discussion 1476
The Storm Prediction Center issued this mesoscale discussion at Aug 11, 2021, 9:52 AM CDT for 4 states. It was in force for 83 min.
The area
The outline as issued.
The facts
- Issued
- Aug 11, 2021, 9:52 AM CDT (14:52 UTC)
- Expired
- Aug 11, 2021, 11:15 AM CDT
- In force
- 83 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 422
All 45 counties
Cook County, IL, DuPage County, IL, Grundy County, IL, Kane County, IL, Kankakee County, IL, Lake County, IL, Will County, IL, Adams County, IN, Allen County, IN, Carroll County, IN, Cass County, IN, DeKalb County, IN, Elkhart County, IN, Fulton County, IN, Huntington County, IN, Jasper County, IN, Kosciusko County, IN, LaGrange County, IN, Lake County, IN, LaPorte County, IN, Marshall County, IN, Miami County, IN, Newton County, IN, Noble County, IN, Porter County, IN, Pulaski County, IN, Saint Joseph County, IN, Starke County, IN, Steuben County, IN, Wabash County, IN, Wells County, IN, White County, IN, Whitley County, IN, Berrien County, MI, Branch County, MI, Calhoun County, MI, Cass County, MI, Hillsdale County, MI, Jackson County, MI, Kalamazoo County, MI, Saint Joseph County, MI, Van Buren County, MI, Defiance County, OH, Paulding County, OH, Williams County, OH
The radar
The Chicago radar (KLOT), 96 km from the middle of the area, began a volume at 14:54 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, 2.9 hours before the alert went out and 203 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.
415
ACUS11 KWNS 111452
SWOMCD
SPC MCD 111452
MIZ000-OHZ000-INZ000-ILZ000-111615-
Mesoscale Discussion 1476
NWS Storm Prediction Center Norman OK
0952 AM CDT Wed Aug 11 2021
Areas affected...Portions of northeastern IL...northern
IN...southern Lower MI...and far northwestern OH
Concerning...Severe Thunderstorm Watch 422...
Valid 111452Z - 111615Z
The severe weather threat for Severe Thunderstorm Watch 422
continues.
SUMMARY...A damaging wind threat continues in the short term with
storms approaching Chicago. A downstream watch may be needed soon if
storms maintain their intensity this morning.
DISCUSSION...Multiple measured severe wind gusts up to 64 mph have
been observed with a small bowing cluster moving eastward across
northern IL this morning. Recent VWPs and velocity data from KLOT
show evidence of a rear-inflow jet, and the potential for 60-75 mph
wind gusts will likely continue in the short term as this cluster
approaches downtown Chicago within the next 30 minutes. With mostly
clear skies ahead of this convection across northern IN and southern
Lower MI, the already moist low-level airmass downstream should
continue to destabilize over the next couple of hours. The presence
of modestly enhanced mid-level flow should support 30-40 kt of
deep-layer shear, and 2000-3000 J/kg of MLCAPE will likely exist as
well. There is still some uncertainty if the ongoing cluster will be
able to maintain its intensity with eastward extent this morning.
Still, if current trends continue, then a downstream Severe
Thunderstorm Watch may need to be considered soon for parts of
northern IN, southern Lower MI, and vicinity given the current rapid
forward speed of the cluster.
..Gleason/Thompson.. 08/11/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...IWX...GRR...IND...LOT...
LAT...LON 41198848 41598841 41888851 42198842 42368618 42348438
41008445 40528515 40578701 41198848SPC 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, 8:34 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, 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 |
| Aug 11, 11:48 AM CDT | Mesoscale Discussion | SPC | Menominee | 117 min |
| Aug 11, 12:17 PM CDT | Tornado Watch | SPC | Delta, Menominee | 8 hr |
| Aug 11, 1:12 PM CDT | Mesoscale Discussion | SPC | Genesee, Huron, Lapeer, Lenawee, Livingston, Macomb and 9 more | 93 min |
| Aug 11, 1:32 PM CDT | Severe Thunderstorm Watch | SPC | Bay, Genesee, Huron, Lapeer, Lenawee, Livingston and 11 more | 4 hr |
| Aug 11, 3:20 PM CDT | Mesoscale Discussion | SPC | Alcona, Alpena, Antrim, Benzie, Cheboygan, Crawford and 13 more | 115 min |
| Aug 11, 3:48 PM CDT | Severe Thunderstorm Watch | SPC | Alcona, Alpena, Antrim, Arenac, Benzie, Charlevoix and 17 more | 3 hr |
| Aug 11, 6:45 PM CDT | Mesoscale Discussion | SPC | Allegan, Barry, Calhoun, Cass, Clinton, Eaton and 15 more | 90 min |
| Aug 11, 8:31 AM CDT | Mesoscale Discussion | SPC | Ashland, Ashtabula, Carroll, Columbiana, Coshocton, Crawford and 19 more | 89 min |
| Aug 11, 10:50 AM CDT | Mesoscale Discussion | SPC | Carroll, Columbiana, Harrison, Jefferson, Mahoning, Trumbull | 115 min |
| Aug 11, 3:24 PM CDT | Mesoscale Discussion | SPC | Athens, Belmont, Carroll, Clinton, Columbiana, Coshocton and 31 more | 96 min |
| Aug 11, 3:57 PM CDT | Severe Thunderstorm Watch | SPC | Ashtabula, Belmont, Carroll, Columbiana, Coshocton, Geauga and 13 more | 3 hr |
Nearby
Mesoscale Discussions in Indiana, 2021Mesoscale Discussions in Michigan, 2021Mesoscale Discussions in Illinois, 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.