Alert archive / Illinois / Mesoscale Discussions in 2021
Mesoscale Discussion 1835
The Storm Prediction Center issued this mesoscale discussion at Oct 11, 2021, 6:09 PM CDT for 19 counties in Illinois. It was in force for 96 min.
The area
The outline as issued.
The facts
- Issued
- Oct 11, 2021, 6:09 PM CDT (23:09 UTC)
- Expired
- Oct 11, 2021, 7:45 PM CDT
- In force
- 96 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 521
Counties Boone County, IL, Champaign County, IL, Coles County, IL, Cook County, IL, DeKalb County, IL, Douglas County, IL, DuPage County, IL, Edgar County, IL, Ford County, IL, Grundy County, IL, Iroquois County, IL, Kane County, IL, Kankakee County, IL, Kendall County, IL, Lake County, IL, LaSalle County, IL, Lee County, IL, Vermilion County, IL, Will County, IL
The radar
The Lincoln radar (KILX), 99 km from the middle of the area, began a volume at 23:09 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 12:00Z, 11.2 hours before the alert went out and 63 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
- 287 J/kg
- Mixed-layer CIN
- -72 J/kg
- Mixed-layer LCL
- 867 m above ground
- 0-6 km bulk shear
- 52 kt
- 0-1 km storm-relative helicity
- 206 m²/s²
- 0-3 km storm-relative helicity
- 230 m²/s²
- Significant tornado parameter
- 0.3
- Supercell composite
- 1.3
The text
As transmitted.
651
ACUS11 KWNS 112309
SWOMCD
SPC MCD 112309
ILZ000-120045-
Mesoscale Discussion 1835
NWS Storm Prediction Center Norman OK
0609 PM CDT Mon Oct 11 2021
Areas affected...central through northeast Illinois
Concerning...Tornado Watch 521...
Valid 112309Z - 120045Z
The severe weather threat for Tornado Watch 521 continues.
SUMMARY...Threat for locally strong to severe gusts and a few brief
tornadoes will persist from central and northern IL through early
evening.
DISCUSSION...An arcing line storms with embedded bowing segments and
occasional meso-vortices continues moving northeast through central
and north central IL at 35-40 kt. The activity is moving through a
relatively narrow instability corridor with 500-1000 J/kg MLCAPE.
Despite the somewhat marginal thermodynamic environment, vertical
wind profiles continue to exhibit large low-level hodographs with
250-300 m2/s2 storm relative helicity as well as 50+ kt effective
bulk shear. The downstream environment across northeast IL will
remain favorable for occasional embedded organized structures
through early evening. Storms will eventually pose a severe threat
for the Chicago metro area near or shortly after 00Z.
..Dial.. 10/11/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LOT...ILX...DVN...
LAT...LON 39348833 40068822 40648830 41218883 41598952 42388905
42178750 39548763 39348833SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Oct 11, 9:06 AM CDT | Mesoscale Discussion | SPC | Adams, Bond, Brown, Calhoun, Cass, Christian and 30 more | 2 hr |
| Oct 11, 12:37 PM CDT | Mesoscale Discussion | SPC | Boone, Bureau, Cook, DeKalb, DuPage, Grundy and 18 more | 113 min |
| Oct 11, 3:10 PM CDT | Tornado Watch | SPC | Boone, Bureau, Carroll, Cass, Champaign, Christian and 45 more | 6 hr |
| Oct 11, 3:37 PM CDT | Mesoscale Discussion | SPC | LaSalle, Marshall, Mason, Menard, Peoria, Putnam and 3 more | 83 min |
Nearby
Mesoscale 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.