Alert archive / Wisconsin / Mesoscale Discussions in 2021
Mesoscale Discussion 1435
The Storm Prediction Center issued this mesoscale discussion at Aug 7, 2021, 5:02 PM CDT for 4 counties in Wisconsin. It was in force for 58 min.
The area
The outline as issued.
The facts
- Issued
- Aug 7, 2021, 5:02 PM CDT (22:02 UTC)
- Expired
- Aug 7, 2021, 6:00 PM CDT
- In force
- 58 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 413
Counties Green County, WI, Iowa County, WI, Rock County, WI, Walworth County, WI
The radar
The Milwaukee radar (KMKX), 66 km from the middle of the area, began a volume at 22:03 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, 10.0 hours before the alert went out and 164 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
- 1645 J/kg
- Mixed-layer CIN
- -79 J/kg
- Mixed-layer LCL
- 1006 m above ground
- 0-6 km bulk shear
- 20 kt
- 0-1 km storm-relative helicity
- 39 m²/s²
- 0-3 km storm-relative helicity
- 37 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
059
ACUS11 KWNS 072203
SWOMCD
SPC MCD 072202
WIZ000-072300-
Mesoscale Discussion 1435
NWS Storm Prediction Center Norman OK
0502 PM CDT Sat Aug 07 2021
Areas affected...southern Wisconsin
Concerning...Severe Thunderstorm Watch 413...
Valid 072202Z - 072300Z
The severe weather threat for Severe Thunderstorm Watch 413
continues.
SUMMARY...A localized corridor favorable for a couple tornadoes may
evolve across portions of southern Wisconsin and WW413.
DISCUSSION...As of 2150 UTC, regional radar data showed several
severe storms ongoing near an MCV and modified effective front
across southern Wisconsin. Along this boundary, locally backed
surface winds are supporting enlarged low-level hodographs favorable
for supercells. SPC mesoanalysis and regional VWPs indicated 300-400
m2/s2 of ESRH is present along the boundary while to the south, a
moderately unstable airmass 2500-3000 J/kg of MLCAPE resides.
Temperatures in the upper 80s and dewpoints in the 70s F will
continue to support robust updraft development along the southern
side of the MCV this afternoon. Given the favorable shear profiles,
a corridor of greater severe threat will continue to evolve across
southern portions of WW413 ahead of a tornadic supercell in Grant
County Wisconsin. Here, a couple tornadoes and damaging wind gusts
will be possible over the next one to two hours.
..Lyons.. 08/07/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MKX...ARX...
LAT...LON 42778867 42688849 42528852 42508891 42588942 42719002
42879039 43129066 43269020 43098958 42978905 42888886
42778867SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 7, 11:03 AM CDT | Mesoscale Discussion | SPC | Crawford, Grant, Iowa, La Crosse, Richland, Sauk and 1 more | 2 hr |
| Aug 7, 3:46 PM CDT | Mesoscale Discussion | SPC | Columbia, Crawford, Dane, Grant, Green, Iowa and 5 more | 119 min |
| Aug 7, 4:36 PM CDT | Severe Thunderstorm Watch | SPC | Columbia, Dane, Dodge, Green, Iowa, Jefferson and 5 more | 4 hr |
Nearby
Mesoscale 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.