Alert archive / Wisconsin / Mesoscale Discussions in 2021
Mesoscale Discussion 993
The Storm Prediction Center issued this mesoscale discussion at Jun 18, 2021, 1:34 AM CDT for Allamakee County, Iowa; Houston County, Minnesota; 15 counties in Wisconsin. It was in force for 116 min.
The area
The outline as issued.
The facts
- Issued
- Jun 18, 2021, 1:34 AM CDT (06:34 UTC)
- Expired
- Jun 18, 2021, 3:30 AM CDT
- In force
- 116 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 278
Counties Allamakee County, IA, Houston County, MN, Columbia County, WI, Crawford County, WI, Dane County, WI, Dodge County, WI, Fond du Lac County, WI, Green Lake County, WI, Iowa County, WI, Jefferson County, WI, Marquette County, WI, Ozaukee County, WI, Richland County, WI, Sauk County, WI, Vernon County, WI, Washington County, WI, Waukesha County, WI
The radar
The La Crosse radar (KARX), 115 km from the middle of the area, began a volume at 06:36 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
Green Bay/Straub, WI (KGRB), launched 00:00Z, 6.6 hours before the alert went out and 186 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
- 52 J/kg
- Mixed-layer CIN
- -285 J/kg
- Mixed-layer LCL
- 1895 m above ground
- 0-6 km bulk shear
- 45 kt
- 0-1 km storm-relative helicity
- 310 m²/s²
- 0-3 km storm-relative helicity
- 397 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.3
The text
As transmitted.
000
ACUS11 KWNS 180634
SWOMCD
SPC MCD 180634
WIZ000-IAZ000-MNZ000-180830-
Mesoscale Discussion 0993
NWS Storm Prediction Center Norman OK
0134 AM CDT Fri Jun 18 2021
Areas affected...Far Southeast Minnesota...Far Northeast
Iowa...South-central Wisconsin
Concerning...Severe Thunderstorm Watch 278...
Valid 180634Z - 180830Z
The severe weather threat for Severe Thunderstorm Watch 278
continues.
SUMMARY...A threat for large hail and isolated wind damage will
likely continue for a few more hours. The threat will probably be
greatest across south-central Wisconsin where a cluster of strong
thunderstorms is ongoing. The storms are expected to decrease in
intensity as they move eastward toward Lake Michigan where
instability is weaker.
DISCUSSION...The latest surface analysis shows a 1004 mb low over
far northeast Iowa with a quasi-stationary front extending eastward
across south-central Wisconsin. An east-to-west line of strong to
severe thunderstorms is ongoing near the front. The RAP is showing
moderate instability across south-central Wisconsin with generally
weaker instability with eastward extent. MUCAPE is estimated near
2500 J/Kg in southwest Wisconsin and near 1000 J/kg in southeast
Wisconsin. Effective shear is estimated near 50 kt across much of
south-central Wisconsin which will likely support a severe threat
for a few more hours. The instability, shear and steep mid-level
lapse rates evident on forecast soundings, will be favorable for
large hail with the stronger updrafts. Concerning the wind-damage
potential, the RAP is showing CIN values in south-central Wisconsin
in the -200 to -300 J/kg range. This will make it difficult for the
stronger storms to produce wind damage. Any wind-damage potential
should remain relatively isolated.
..Broyles.. 06/18/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MKX...ARX...
LAT...LON 43918999 43859153 43519189 43079179 42929141 42948930
42938769 43328741 43768786 43918999SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 17, 7:02 PM CDT | Mesoscale Discussion | SPC | Allamakee, Howard, Mitchell, Winnebago, Winneshiek, Worth | 88 min |
| Jun 17, 9:01 PM CDT | Mesoscale Discussion | SPC | Allamakee, Howard, Mitchell, Winneshiek | 89 min |
| Jun 17, 10:01 PM CDT | Severe Thunderstorm Watch | SPC | Allamakee, Bremer, Butler, Cerro Gordo, Chickasaw, Clayton and 10 more | 6 hr |
| Jun 17, 10:52 PM CDT | Mesoscale Discussion | SPC | Allamakee, Howard, Winneshiek | 83 min |
| Jun 17, 7:22 PM CDT | Severe Thunderstorm Watch | SPC | Blue Earth, Brown, Dakota, Faribault, Freeborn, Goodhue and 9 more | 4 hr |
| Jun 18, 5:03 PM CDT | Mesoscale Discussion | SPC | Becker, Beltrami, Cass, Clay, Clearwater, Crow Wing and 9 more | 87 min |
Nearby
Mesoscale Discussions in Wisconsin, 2021Mesoscale Discussions in Iowa, 2021Mesoscale Discussions in Minnesota, 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.