Alert archive / Illinois / Mesoscale Discussions in 2021
Mesoscale Discussion 1467
The Storm Prediction Center issued this mesoscale discussion at Aug 10, 2021, 5:51 PM CDT for 13 counties in Illinois; 6 counties in Iowa; 13 counties in Wisconsin. It was in force for 84 min.
The area
The outline as issued.
The facts
- Issued
- Aug 10, 2021, 5:51 PM CDT (22:51 UTC)
- Expired
- Aug 10, 2021, 7:15 PM CDT
- In force
- 84 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 419...420
All 32 counties
Cedar County, IA, Clinton County, IA, Jackson County, IA, Jones County, IA, Muscatine County, IA, Scott County, IA, Boone County, IL, Carroll County, IL, DeKalb County, IL, DuPage County, IL, Jo Daviess County, IL, Kane County, IL, Lee County, IL, McHenry County, IL, Ogle County, IL, Rock Island County, IL, Stephenson County, IL, Whiteside County, IL, Winnebago County, IL, Columbia County, WI, Dane County, WI, Dodge County, WI, Green County, WI, Iowa County, WI, Jefferson County, WI, Kenosha County, WI, Lafayette County, WI, Milwaukee County, WI, Rock County, WI, Sauk County, WI, Walworth County, WI, Waukesha County, WI
The radar
The Quad Cities radar (KDVN), 110 km from the middle of the area, began a volume at 22:51 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, 10.9 hours before the alert went out and 106 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
- 3755 J/kg
- Mixed-layer CIN
- -67 J/kg
- Mixed-layer LCL
- 819 m above ground
- 0-6 km bulk shear
- 12 kt
- 0-1 km storm-relative helicity
- -37 m²/s²
- 0-3 km storm-relative helicity
- 4 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
644
ACUS11 KWNS 102251
SWOMCD
SPC MCD 102251
ILZ000-WIZ000-IAZ000-110015-
Mesoscale Discussion 1467
NWS Storm Prediction Center Norman OK
0551 PM CDT Tue Aug 10 2021
Areas affected...Portions of Iowa...Illinois and Wisconsin.
Concerning...Severe Thunderstorm Watch 419...420...
Valid 102251Z - 110015Z
The severe weather threat for Severe Thunderstorm Watch 419, 420
continues.
SUMMARY...A well-developed line of thunderstorms will continue to
pose a risk for damaging winds as it tracks east/southeast across
WW419 and WW420.
DISCUSSION...As of 2245 UTC, SPC mesonalysis shows extreme
instability (MLCAPE of 4000-5000 J/kg) is in place with little
remaining convective inhibition ahead of a line of severe
thunderstorms across eastern Iowa, western Illinois and southern
Wisconsin. Within the line, recent radar and satellite trends
indicate a corridor of enhanced wind-damage potential may evolve
across the southern Wisconsin and northern Illinois border region
over the next several hours. Surface obs immediately behind the line
show stronger cold pool development is underway. Greater lift along
the cold pool may contribute to a stronger rear-inflow jet and
bowing out of the line segment with time. This is also corroborated
by several recent reports of wind damage and a measured wind gust of
70 mph in Platteville, WI. Additional damaging wind gusts, some
potentially 70+ mph, appear possible as this segment of the line
continues to the east along the Illinois/Wisconsin border.
Farther south across eastern Iowa, storms have struggled to maintain
intensity likely due to weaker effective shear below 25 kts.
Additional development ahead of the main line has been noted within
the very unstable airmass, and should continue into this evening.
While somewhat less favorable for severe wind gusts given the weaker
vertical shear and limited organization, the additional storm
development will likely reinforce the cold pool associated with
previous convection and support a few damaging wind gusts as it
track to the south and east into northwestern Illinois
..Lyons.. 08/10/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LOT...MKX...DVN...ARX...
LAT...LON 42029165 42599062 43239045 43479025 43618978 43508869
43218794 42858784 42328785 41808788 41598922 41229098
41439144 41859167 42029165SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 9, 8:33 PM CDT | Mesoscale Discussion | SPC | Bureau, Knox, LaSalle, Livingston, Marshall, Peoria and 4 more | 87 min |
| Aug 10, 10:45 AM CDT | Mesoscale Discussion | SPC | Adams, Bond, Brown, Calhoun, Clinton, Greene and 9 more | 3 hr |
| Aug 10, 2:08 PM CDT | Severe Thunderstorm Watch | SPC | Henderson, Mercer, Rock Island, Warren | 6 hr |
| Aug 10, 2:20 PM CDT | Mesoscale Discussion | SPC | Alexander, Bond, Clay, Clinton, Edwards, Franklin and 21 more | 2 hr |
| Aug 10, 3:10 PM CDT | Mesoscale Discussion | SPC | Boone, Carroll, DeKalb, Jo Daviess, Kane, Lake and 6 more | 2 hr |
| Aug 10, 3:47 PM CDT | Severe Thunderstorm Watch | SPC | Boone, Bureau, Carroll, Cook, DeKalb, DuPage and 15 more | 6 hr |
| Aug 10, 1:12 PM CDT | Mesoscale Discussion | SPC | Appanoose, Benton, Black Hawk, Bremer, Buchanan, Butler and 35 more | 93 min |
| Aug 10, 12:02 PM CDT | Mesoscale Discussion | SPC | Ashland, Bayfield, Iron, Sawyer, Vilas | 88 min |
Nearby
Mesoscale Discussions in Illinois, 2021Mesoscale Discussions in Wisconsin, 2021Mesoscale Discussions in Iowa, 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.