Alert archive / Wisconsin / Mesoscale Discussions in 2021
Mesoscale Discussion 1623
The Storm Prediction Center issued this mesoscale discussion at Aug 27, 2021, 7:59 PM CDT for Allamakee County, Clayton County, Fayette County, Iowa; 4 counties in Wisconsin. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 27, 2021, 7:59 PM CDT (00:59 UTC)
- Expired
- Aug 27, 2021, 10:00 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 465
Counties Allamakee County, IA, Clayton County, IA, Fayette County, IA, Crawford County, WI, Grant County, WI, Iowa County, WI, Lafayette County, WI
The radar
The La Crosse radar (KARX), 96 km from the middle of the area, began a volume at 01:01 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 00:00Z, 1.0 hours before the alert went out and 159 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
- 995 J/kg
- Mixed-layer CIN
- -68 J/kg
- Mixed-layer LCL
- 1707 m above ground
- 0-6 km bulk shear
- 26 kt
- 0-1 km storm-relative helicity
- 53 m²/s²
- 0-3 km storm-relative helicity
- 148 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 1.3
The text
As transmitted.
694
ACUS11 KWNS 280059
SWOMCD
SPC MCD 280059
WIZ000-ILZ000-IAZ000-280300-
Mesoscale Discussion 1623
NWS Storm Prediction Center Norman OK
0759 PM CDT Fri Aug 27 2021
Areas affected...Northeast Iowa and southwest Wisconsin
Concerning...Tornado Watch 465...
Valid 280059Z - 280300Z
The severe weather threat for Tornado Watch 465 continues.
SUMMARY...The tornado threat in WW 465 will be maximized with a
supercell thunderstorm moving into southwestern Wisconsin.
DISCUSSION...The greatest tornado threat in WW 465 will exist with a
supercell storm moving along the Allamakee/Clayton County (IA)
border. This storm will impact parts of Crawford/Grant Counties (WI)
within the next 1-2 hours. Moderate buoyancy remains ahead of this
storm with surface winds still backed to SSE.
In southeastern Minnesota, thunderstorms have increased in coverage,
but they are likely slightly elevated above the cooler air that has
remained in place. These storms could periodically intensify given
modest mid-level lapse rates and around 40 kts of shear. Damaging
winds and isolated large hail would be the main threats.
The low-level jet is forecast to increase into southern Wisconsin as
the evening progresses. This may promote greater storm coverage from
southeastern Minnesota into southern Wisconsin. This sort of
scenario would likely favor a cluster of storms slowly sagging south
and east with an accompanying damaging wind threat.
..Wendt.. 08/28/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MKX...DVN...ARX...
LAT...LON 42889204 42959204 43159197 43369159 43479127 43409051
43018990 42628996 42419059 42469080 42889204SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 27, 9:57 PM CDT | Mesoscale Discussion | SPC | Allamakee, Bremer, Chickasaw, Clayton, Fayette, Floyd and 3 more | 93 min |
| Aug 28, 2:43 PM CDT | Mesoscale Discussion | SPC | Lyon, Osceola, Plymouth, Sioux | 3 hr |
| Aug 28, 3:57 PM CDT | Severe Thunderstorm Watch | SPC | Lyon, O'Brien, Osceola, Plymouth, Sioux, Woodbury | 7 hr |
| Aug 28, 5:27 PM CDT | Mesoscale Discussion | SPC | Emmet | 63 min |
| Aug 28, 9:39 AM CDT | Mesoscale Discussion | SPC | Ashland, Barron, Bayfield, Burnett, Douglas, Iron and 5 more | 2 hr |
| Aug 28, 10:34 AM CDT | Tornado Watch | SPC | Ashland, Barron, Bayfield, Burnett, Chippewa, Douglas and 8 more | 4 hr |
| Aug 28, 1:13 PM CDT | Mesoscale Discussion | SPC | Ashland, Barron, Bayfield, Burnett, Douglas, Iron and 5 more | 2 hr |
Nearby
Mesoscale 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.