Alert archive / Illinois / Mesoscale Discussions in 2021
Mesoscale Discussion 1833
The Storm Prediction Center issued this mesoscale discussion at Oct 11, 2021, 3:37 PM CDT for 9 counties in Illinois. It was in force for 83 min.
The area
The outline as issued.
The facts
- Issued
- Oct 11, 2021, 3:37 PM CDT (20:37 UTC)
- Expired
- Oct 11, 2021, 5:00 PM CDT
- In force
- 83 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 521
Counties LaSalle County, IL, Marshall County, IL, Mason County, IL, Menard County, IL, Peoria County, IL, Putnam County, IL, Stark County, IL, Tazewell County, IL, Woodford County, IL
The radar
The Lincoln radar (KILX), 94 km from the middle of the area, began a volume at 20:38 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
Davenport, (KDVN), launched 12:00Z, 8.6 hours before the alert went out and 114 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 798 m above ground
- 0-6 km bulk shear
- 38 kt
- 0-1 km storm-relative helicity
- 108 m²/s²
- 0-3 km storm-relative helicity
- 126 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
736 ACUS11 KWNS 112037 SWOMCD SPC MCD 112037 ILZ000-112200- Mesoscale Discussion 1833 NWS Storm Prediction Center Norman OK 0337 PM CDT Mon Oct 11 2021 Areas affected...central and north-central IL Concerning...Tornado Watch 521... Valid 112037Z - 112200Z The severe weather threat for Tornado Watch 521 continues. SUMMARY...The risk for wind damage and a couple of transient mesovortices capable of a short-lived/weak tornado, will probably maximize over the next 1-2 hours as a bowing squall line quickly moves northeastward across north-central IL. DISCUSSION...Radar mosaic shows a maturing squall line in the vicinity of a surface low over west-central IL. The airmass over the northern third of IL is moist (mid 60s surface dewpoints) but clouds have tempered overall destabilization this afternoon. Nonetheless, weak buoyancy noted in RAP forecast soundings will aid in storm vigor as the squall line moves northeast across central and northwest IL through the early evening. The primary risk will be damaging gusts in association with surging areas of the squall line, but a short-lived tornado is possible with more intense eddies/mesovortices that become sustained as this activity moves across the I-74 and I-80 corridors during the next few hours. One limitation that may limit the overall severe risk is weaker shear evident at the Davenport, IA 88D VAD and this may limit the severe risk near the MS River. ..Smith.. 10/11/2021 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LOT...ILX...DVN... LAT...LON 41019014 41588921 41468861 41068849 39868988 41019014
SPC 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, 6:09 PM CDT | Mesoscale Discussion | SPC | Boone, Champaign, Coles, Cook, DeKalb, Douglas and 13 more | 96 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.