Alert archive / Wisconsin / Mesoscale Discussions in 2021
Mesoscale Discussion 1379
The Storm Prediction Center issued this mesoscale discussion at Jul 28, 2021, 8:59 PM CDT for 6 counties in Wisconsin. It was in force for 61 min.
The area
The outline as issued.
The facts
- Issued
- Jul 28, 2021, 8:59 PM CDT (01:59 UTC)
- Expired
- Jul 28, 2021, 10:00 PM CDT
- In force
- 61 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 399
Counties Chippewa County, WI, Clark County, WI, Eau Claire County, WI, Jackson County, WI, Monroe County, WI, Trempealeau County, WI
The radar
The La Crosse radar (KARX), 103 km from the middle of the area, began a volume at 01:57 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, 2.0 hours before the alert went out and 195 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.
013
ACUS11 KWNS 290159
SWOMCD
SPC MCD 290159
WIZ000-290300-
Mesoscale Discussion 1379
NWS Storm Prediction Center Norman OK
0859 PM CDT Wed Jul 28 2021
Areas affected...Portions of west-central Wisconsin
Concerning...Severe Thunderstorm Watch 399...
Valid 290159Z - 290300Z
The severe weather threat for Severe Thunderstorm Watch 399
continues.
SUMMARY...An enhanced corridor of strong wind gusts is developing in
northern Chippewa county.
DISCUSSION...Two strong supercells in Barron and Risk counties have
started to congeal and based on base velocity trends it appears a
cold pool and gust front may be starting to develop. The downstream
airmass is very unstable with a gradient of 2000 to 4000 J/kg
MLCAPE. The 00Z MPX RAOB was very favorable for high end damaging
wind gusts with extreme instability and nearly 50 knots of effective
shear and 35 knots of 0 to 3km shear. In addition, 30 to 35 knots of
flow was measured below 1km with the KMPX VWP suggesting winds may
have now strengthened to 40 knots. Therefore, in addition to the
high end damaging wind potential in this swath, there will also be
potential for some embedded QLCS tornadic vorticies.
..Bentley.. 07/29/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...ARX...MPX...
LAT...LON 45169098 44939064 44129042 43869066 43939118 44529159
45019179 45179165 45209141 45189122 45169098SPC 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, 9:51 PM CDT | Mesoscale Discussion | SPC | Eau Claire, Jackson, Monroe | 54 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.