Alert archive / Illinois / Mesoscale Discussions in 2021
Mesoscale Discussion 1291
The Storm Prediction Center issued this mesoscale discussion at Jul 14, 2021, 11:17 PM CDT for 12 counties in Illinois; Clinton County, Muscatine County, Scott County, Iowa; Rock County, Wisconsin. It was in force for 58 min.
The area
The outline as issued.
The facts
- Issued
- Jul 14, 2021, 11:17 PM CDT (04:17 UTC)
- Expired
- Jul 15, 2021, 12:15 AM CDT
- In force
- 58 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 379
Counties Clinton County, IA, Muscatine County, IA, Scott County, IA, Boone County, IL, Carroll County, IL, DeKalb County, IL, Henry County, IL, Lee County, IL, McHenry County, IL, Mercer County, IL, Ogle County, IL, Rock Island County, IL, Stephenson County, IL, Whiteside County, IL, Winnebago County, IL, Rock County, WI
The radar
The Quad Cities radar (KDVN), 58 km from the middle of the area, began a volume at 04:17 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
Davenport, (KDVN), launched 00:00Z, 4.3 hours before the alert went out and 52 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
- 2569 J/kg
- Mixed-layer CIN
- -10 J/kg
- Mixed-layer LCL
- 832 m above ground
- 0-6 km bulk shear
- 38 kt
- 0-1 km storm-relative helicity
- 253 m²/s²
- 0-3 km storm-relative helicity
- 346 m²/s²
- Significant tornado parameter
- 3.2
- Supercell composite
- 23.4
The text
As transmitted.
968 ACUS11 KWNS 150417 SWOMCD SPC MCD 150417 WIZ000-ILZ000-IAZ000-150515- Mesoscale Discussion 1291 NWS Storm Prediction Center Norman OK 1117 PM CDT Wed Jul 14 2021 Areas affected...Extreme eastern IA...northern IL...extreme southeast WI Concerning...Tornado Watch 379... Valid 150417Z - 150515Z The severe weather threat for Tornado Watch 379 continues. SUMMARY...Strong/severe convection will continue to sag east-southeast across ww379. Locally damaging winds may become the primary concern. Some consideration is being given to a new watch immediately downstream across northern IL. DISCUSSION...LLJ continues to strengthen as it veers strongly southwest ahead of the primary convection. Deeper wind profiles suggest a more linear/bow-type storm mode should be the primary concern as SW-NE oriented corridor of convection shifts east at roughly 25kt. As surface temperatures cool into the mid 70s, forecast soundings suggest thunderstorms will become increasingly elevated, likely rooted near 925mb. Given the increasingly linear storm mode, and decoupling of the boundary layer, the main concern should be wind as the squall line advances across northern IL tonight. ..Darrow.. 07/15/2021 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LOT...ILX...MKX...DVN... LAT...LON 41469128 42738935 42648819 41658890 41029066 41469128
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 14, 9:15 PM CDT | Mesoscale Discussion | SPC | Carroll, Jo Daviess, Ogle, Stephenson, Winnebago | 90 min |
| Jul 14, 11:57 PM CDT | Severe Thunderstorm Watch | SPC | Boone, Bureau, DeKalb, Grundy, Henry, Kane and 7 more | 3 hr |
| Jul 15, 2:14 AM CDT | Mesoscale Discussion | SPC | Boone, Bureau, DeKalb, DuPage, Grundy, Kane and 12 more | 61 min |
| Jul 15, 1:39 PM CDT | Mesoscale Discussion | SPC | Brown, Cass, Champaign, Christian, Coles, DeWitt and 24 more | 2 hr |
| Jul 14, 8:35 PM CDT | Mesoscale Discussion | SPC | Benton, Black Hawk, Buchanan, Fayette, Grundy, Jasper and 5 more | 25 min |
Nearby
Mesoscale Discussions in Illinois, 2021Mesoscale Discussions in Iowa, 2021Mesoscale Discussions in Wisconsin, 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.