Alert archive / Illinois / Mesoscale Discussions in 2021
Mesoscale Discussion 1831
The Storm Prediction Center issued this mesoscale discussion at Oct 11, 2021, 9:06 AM CDT for 36 counties in Illinois; 17 counties in Missouri. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Oct 11, 2021, 9:06 AM CDT (14:06 UTC)
- Expired
- Oct 11, 2021, 11:30 AM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 60%
All 53 counties
Adams County, IL, Bond County, IL, Brown County, IL, Calhoun County, IL, Cass County, IL, Christian County, IL, Clinton County, IL, DeWitt County, IL, Fulton County, IL, Greene County, IL, Hancock County, IL, Henderson County, IL, Jersey County, IL, Knox County, IL, Logan County, IL, Macon County, IL, Macoupin County, IL, Madison County, IL, Mason County, IL, McDonough County, IL, McLean County, IL, Menard County, IL, Monroe County, IL, Montgomery County, IL, Morgan County, IL, Peoria County, IL, Pike County, IL, Randolph County, IL, Saint Clair County, IL, Sangamon County, IL, Schuyler County, IL, Scott County, IL, Tazewell County, IL, Warren County, IL, Washington County, IL, Woodford County, IL, Audrain County, MO, Callaway County, MO, City of Saint Louis, MO, Franklin County, MO, Gasconade County, MO, Jefferson County, MO, Lincoln County, MO, Marion County, MO, Monroe County, MO, Montgomery County, MO, Pike County, MO, Ralls County, MO, Saint Charles County, MO, Saint Francois County, MO, Saint Louis County, MO, Sainte Genevieve County, MO, Warren County, MO
The radar
The St Louis radar (KLSX), 81 km from the middle of the area, began a volume at 14:09 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, 2.1 hours before the alert went out and 191 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.
018
ACUS11 KWNS 111406
SWOMCD
SPC MCD 111406
ILZ000-MOZ000-IAZ000-111630-
Mesoscale Discussion 1831
NWS Storm Prediction Center Norman OK
0906 AM CDT Mon Oct 11 2021
Areas affected...eastern MO...western and central IL
Concerning...Severe potential...Watch possible
Valid 111406Z - 111630Z
Probability of Watch Issuance...60 percent
SUMMARY...Trends will be monitored this morning for surface-based
thunderstorm development. The initial area of concern will be over
central MO and areas northeastward towards the MS River. A tornado
watch will likely be needed by midday for portions of eastern MO
into western IL. It is uncertain whether surface-based storms and a
subsequent tornado risk will develop as far north as extreme eastern
IA.
DISCUSSION...Visible-satellite imagery shows a compact/intense
mid-level shortwave trough over the lower MO Valley. Weak
convection has been maintained this morning within the warm conveyer
belt from southeast MO through the Saint Louis area and into western
IL. A surface trough/windshift is analyzed this morning arcing from
near the low through central and south-central MO. A small area of
cloud breaks is noted in visible-satellite imagery over central MO
where forcing is maximized and over the location of greatest concern
this morning.
Model forecast soundings show gradual destabilization this morning
into the midday hours as temperatures slowly rise into the lower 70s
with a moist boundary layer. Very strong low-level flow noted at
the Saint Louis 88D VAD is resulting in a large low-level hodograph
(400+ m2/s2 0-1 km SRH). Once sufficiently strong updrafts can
develop/persist, a severe risk will likely ensue with an isolated
risk for tornadoes and damaging winds being the primary concerns.
..Smith/Hart.. 10/11/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...PAH...ILX...LSX...DVN...
LAT...LON 38659231 39239227 40839106 41139028 41028944 40568880
39668882 37748963 37789059 38409140 38659231SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| 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 |
| Oct 11, 6:09 PM CDT | Mesoscale Discussion | SPC | Boone, Champaign, Coles, Cook, DeKalb, Douglas and 13 more | 96 min |
| Oct 10, 7:19 PM CDT | Mesoscale Discussion | SPC | Bates | 86 min |
| Oct 10, 9:24 PM CDT | Tornado Watch | SPC | Barry, Jasper, Lawrence, McDonald, Newton | 5 hr |
| Oct 10, 11:32 PM CDT | Mesoscale Discussion | SPC | Jasper, McDonald, Newton | 118 min |
| Oct 11, 1:26 AM CDT | Mesoscale Discussion | SPC | Barry, Dade, Greene, Jasper, Lawrence, McDonald and 2 more | 64 min |
| Oct 11, 5:00 AM CDT | Mesoscale Discussion | SPC | Cedar, Christian, Dade, Dallas, Greene, Hickory and 7 more | 2 hr |
Nearby
Mesoscale Discussions in Illinois, 2021Mesoscale Discussions in Missouri, 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.