Alert archive / Illinois / Mesoscale Discussions in 2021
Mesoscale Discussion 1500
The Storm Prediction Center issued this mesoscale discussion at Aug 12, 2021, 2:22 PM CDT for 32 counties in Illinois; 14 counties in Indiana. It was in force for 83 min.
The area
The outline as issued.
The facts
- Issued
- Aug 12, 2021, 2:22 PM CDT (19:22 UTC)
- Expired
- Aug 12, 2021, 3:45 PM CDT
- In force
- 83 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
All 46 counties
Bond County, IL, Cass County, IL, Champaign County, IL, Christian County, IL, Clark County, IL, Clay County, IL, Coles County, IL, Crawford County, IL, Cumberland County, IL, DeWitt County, IL, Douglas County, IL, Edgar County, IL, Effingham County, IL, Fayette County, IL, Greene County, IL, Jasper County, IL, Jersey County, IL, Lawrence County, IL, Logan County, IL, Macon County, IL, Macoupin County, IL, Mason County, IL, Menard County, IL, Montgomery County, IL, Morgan County, IL, Moultrie County, IL, Piatt County, IL, Richland County, IL, Sangamon County, IL, Scott County, IL, Shelby County, IL, Vermilion County, IL, Clay County, IN, Fountain County, IN, Greene County, IN, Hendricks County, IN, Lawrence County, IN, Monroe County, IN, Montgomery County, IN, Morgan County, IN, Owen County, IN, Parke County, IN, Putnam County, IN, Sullivan County, IN, Vermillion County, IN, Vigo County, IN
The radar
The Lincoln radar (KILX), 65 km from the middle of the area, began a volume at 19:26 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, 7.4 hours before the alert went out and 62 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
- 1191 J/kg
- Mixed-layer CIN
- -177 J/kg
- Mixed-layer LCL
- 1149 m above ground
- 0-6 km bulk shear
- 32 kt
- 0-1 km storm-relative helicity
- 140 m²/s²
- 0-3 km storm-relative helicity
- 128 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 3.1
The text
As transmitted.
105
ACUS11 KWNS 121922
SWOMCD
SPC MCD 121922
INZ000-ILZ000-122045-
Mesoscale Discussion 1500
NWS Storm Prediction Center Norman OK
0222 PM CDT Thu Aug 12 2021
Areas affected...Central Illinois into west-central Indiana
Concerning...Severe potential...Watch unlikely
Valid 121922Z - 122045Z
Probability of Watch Issuance...20 percent
SUMMARY...Isolated damaging wind gusts are possible through the
afternoon and evening.
DISCUSSION...Ongoing mid-level convection has been mostly a flash
flood threat as storms were mostly training through the morning and
early afternoon. However, recently outflow has pushed south from
this activity into south-central Illinois where SPC mesoanalysis
shows MLCIN has mostly eroded and a boundary layer cu field has
developed. More robust convection has developed near the interaction
of this outflow with the stronger instability (MLCAPE around 2500 to
3500 J/kg). Effective shear is only around 25 kts per ILX/IND VWP
and given the speed of the outflow, storm organization and
maintenance along the surging outflow boundary may be difficult.
Therefore, isolated damaging wind gusts may occur near storm
collapses, but a more organized severe weather threat seems unlikely
and thus no watch is anticipated.
..Bentley/Thompson.. 08/12/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...IND...LOT...ILX...LSX...
LAT...LON 40289028 40318858 40458767 39928628 38828649 38618838
38828988 39209059 39839090 40289028SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 11, 7:35 PM CDT | Mesoscale Discussion | SPC | Boone, Bureau, Carroll, Cook, DeKalb, DuPage and 20 more | 85 min |
| Aug 11, 8:22 PM CDT | Severe Thunderstorm Watch | SPC | Bureau, Cook, DeKalb, DuPage, Ford, Grundy and 11 more | 8 hr |
| Aug 11, 11:06 PM CDT | Mesoscale Discussion | SPC | Boone, Bureau, Carroll, Cook, DeKalb, DuPage and 15 more | 84 min |
| Aug 12, 3:16 AM CDT | Mesoscale Discussion | SPC | Bureau, Ford, Fulton, Grundy, Iroquois, Kankakee and 16 more | 119 min |
| Aug 12, 5:19 PM CDT | Severe Thunderstorm Watch | SPC | Calhoun, Clinton, Greene, Jersey, Macoupin, Madison and 7 more | 5 hr |
| Aug 12, 6:06 PM CDT | Mesoscale Discussion | SPC | Calhoun, Jersey, Madison, Monroe, Saint Clair | 84 min |
Nearby
Mesoscale Discussions in Illinois, 2021Mesoscale Discussions in Indiana, 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.