Alert archive / Indiana / Mesoscale Discussions in 2021

Mesoscale Discussion 1385

July 29, 202110 counties in Illinois; 13 counties in Indiana; 6 counties in Michigan

The Storm Prediction Center issued this mesoscale discussion at Jul 29, 2021, 3:18 AM CDT for 10 counties in Illinois; 13 counties in Indiana; 6 counties in Michigan. It was in force for 87 min.

The area

The outline as issued.

The facts

Issued: Jul 29, 2021, 3:18 AM CDT (08:18 UTC)
Expired: Jul 29, 2021, 4:45 AM CDT
In force: 87 min
Issued by: the Storm Prediction Center
Concerning: Severe thunderstorm watch 400

All 29 counties

Cook County, IL, DeKalb County, IL, DuPage County, IL, Grundy County, IL, Iroquois County, IL, Kankakee County, IL, Kendall County, IL, LaSalle County, IL, Livingston County, IL, Will 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), 65 km from the middle of the area, began a volume at 08:18 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, 8.3 hours before the alert went out and 206 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

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

Open this sounding in Storm Lab

The text

As transmitted.

259 
ACUS11 KWNS 290818
SWOMCD
SPC MCD 290818 
MIZ000-INZ000-ILZ000-290945-

Mesoscale Discussion 1385
NWS Storm Prediction Center Norman OK
0318 AM CDT Thu Jul 29 2021

Areas affected...Portions of northern IL/IN and southwestern Lower
MI

Concerning...Severe Thunderstorm Watch 400...

Valid 290818Z - 290945Z

The severe weather threat for Severe Thunderstorm Watch 400
continues.

SUMMARY...A strong to severe wind threat continues in the short
term. Storms should gradually weaken with southward extent across
northern Illinois/Indiana later this morning.

DISCUSSION...Both IR cloud tops and radar echo tops associated with
the ongoing MCS across northern IL have recently warmed and
weakened, respectively. Still, a swath of strong to severe wind
gusts (generally 50-65 mph) and related damage reports have occurred
across the Chicago metro area over the past hour or so. The airmass
downstream of this ongoing convection across northern IL/IN and
southwestern Lower MI becomes less unstable with southward extent,
as both surface temperatures and dewpoints slowly decrease. While a
threat for scattered damaging wind gusts will continue in the short
term across this region, current expectations are for the MCS to
continue gradually weakening over the next couple of hours as it
encounters increasing convective inhibition and less instability.
This evolution appears well supported by the past couple of runs of
the HRRR.

..Gleason.. 07/29/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...IWX...GRR...LOT...

LAT...LON   42088885 41838832 41928777 42078727 42448678 42698615
            42468515 42118509 41618529 41128590 40748691 40698795
            40908877 41208905 41858910 42088885

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 29, 12:32 AM CDT	Mesoscale Discussion	SPC	Boone, Carroll, Cook, DeKalb, DuPage, Grundy and 11 more	88 min
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, 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 Indiana, 2021 Mesoscale Discussions in Illinois, 2021 Mesoscale Discussions in Michigan, 2021 Every 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.