Alert archive / Wisconsin / Mesoscale Discussions in 2021
Mesoscale Discussion 1380
The Storm Prediction Center issued this mesoscale discussion at Jul 28, 2021, 9:51 PM CDT for Eau Claire County, Jackson County, Monroe County, Wisconsin. It was in force for 54 min.
The area
The outline as issued.
The facts
- Issued
- Jul 28, 2021, 9:51 PM CDT (02:51 UTC)
- Expired
- Jul 28, 2021, 10:45 PM CDT
- In force
- 54 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 399
Counties Eau Claire County, WI, Jackson County, WI, Monroe County, WI
The radar
The La Crosse radar (KARX), 64 km from the middle of the area, began a volume at 02:56 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
Minneapolis, MN (KMPX), launched 00:00Z, 2.9 hours before the alert went out and 221 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
- 4815 J/kg
- Mixed-layer CIN
- -38 J/kg
- Mixed-layer LCL
- 1185 m above ground
- 0-6 km bulk shear
- 45 kt
- 0-1 km storm-relative helicity
- 374 m²/s²
- 0-3 km storm-relative helicity
- 461 m²/s²
- Significant tornado parameter
- 8.9
- Supercell composite
- 48.1
The text
As transmitted.
820
ACUS11 KWNS 290252
SWOMCD
SPC MCD 290251
WIZ000-290345-
Mesoscale Discussion 1380
NWS Storm Prediction Center Norman OK
0951 PM CDT Wed Jul 28 2021
Areas affected...portions of western Wisconsin.
Concerning...Severe Thunderstorm Watch 399...
Valid 290251Z - 290345Z
The severe weather threat for Severe Thunderstorm Watch 399
continues.
SUMMARY...Very strong winds (80+ mph) likely for the next 1 to 2
hours.
DISCUSSION...A narrow corridor of very intense winds has developed
with a bowing segment along the Chippewa, Eau Claire, and Clark
county lines. The KARX WSR-88D has the best viewing angle for this
storm, but the extreme wind values being sampled at ~6000 feet have
resulted in considerable dealiasing issues with the velocity data at
the 0.5 degree tilt. However, by using higher tilts and other
viewing angles such as KDLH, there is high confidence that winds
between 8 and 10kft are at or above 80 knots. Therefore, areas near
the apex of this bow are likely experiencing surface winds in excess
of 80mph. Given the favorable downstream environment and the fact
that this bowing segment is still early in its life cycle, even
stronger winds are possible as it continues south-southeast over the
next 1 to 2 hours. In fact, the early stages of a bookend vortex may
be starting in eastern Clark county indicating the system is likely
in its maturing stage.
..Bentley.. 07/29/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...ARX...MPX...
LAT...LON 44749137 44799118 44799088 44819070 44209034 43879034
43769044 43779077 44069119 44389127 44749137SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 28, 7:17 PM CDT | Severe Thunderstorm Watch | SPC | Adams, Barron, Brown, Buffalo, Burnett, Calumet and 61 more | 7 hr |
| Jul 28, 8:59 PM CDT | Mesoscale Discussion | SPC | Chippewa, Clark, Eau Claire, Jackson, Monroe, Trempealeau | 61 min |
| Jul 28, 10:17 PM CDT | Mesoscale Discussion | SPC | Buffalo, Dunn, Pepin, Pierce, Saint Croix | 58 min |
| Jul 28, 11:24 PM CDT | Mesoscale Discussion | SPC | Adams, Buffalo, Calumet, Columbia, Crawford, Dane and 34 more | 96 min |
| Jul 29, 1:34 AM CDT | Mesoscale Discussion | SPC | Kenosha, Milwaukee, Racine, Rock, Walworth, Waukesha | 86 min |
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.