Alert archive / Minnesota / Mesoscale Discussions in 2021
Mesoscale Discussion 1381
The Storm Prediction Center issued this mesoscale discussion at Jul 28, 2021, 10:17 PM CDT for 5 counties in Minnesota; 5 counties in Wisconsin. It was in force for 58 min.
The area
The outline as issued.
The facts
- Issued
- Jul 28, 2021, 10:17 PM CDT (03:17 UTC)
- Expired
- Jul 28, 2021, 11:15 PM CDT
- In force
- 58 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 399
Counties Goodhue County, MN, Olmsted County, MN, Wabasha County, MN, Washington County, MN, Winona County, MN, Buffalo County, WI, Dunn County, WI, Pepin County, WI, Pierce County, WI, Saint Croix County, WI
The radar
The La Crosse radar (KARX), 105 km from the middle of the area, began a volume at 03:18 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, 3.3 hours before the alert went out and 123 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.
206
ACUS11 KWNS 290318
SWOMCD
SPC MCD 290317
WIZ000-MNZ000-290415-
Mesoscale Discussion 1381
NWS Storm Prediction Center Norman OK
1017 PM CDT Wed Jul 28 2021
Areas affected...Western Wisconsin and southeast Minnesota
Concerning...Severe Thunderstorm Watch 399...
Valid 290317Z - 290415Z
The severe weather threat for Severe Thunderstorm Watch 399
continues.
SUMMARY...There is an increasing threat for severe (potentially high
end) damaging winds across portions of western Wisconsin and eastern
Minnesota.
DISCUSSION...Recent KARX and KMPX radar trends show an increasing
area of strong winds in St. Croix county with hints of an increasing
rear inflow jet over the past few scans. Given the very unstable
downstream environment (3500 J/kg MLCAPE) and 40 knots of flow at
1km from the KMPX VWP, the environment is primed for very strong
winds. Therefore, as this cluster moves southeast and matures,
hurricane force winds are likely. The current trajectory of this
cluster would bring the threat into portions of southeast Minnesota
which are not currently in watch 399. Therefore, after collaboration
with the local forecast office in La Crosse, Wisconsin, watch 399
will be expanded into southeastern Minnesota and northeastern Iowa.
..Bentley.. 07/29/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...ARX...MPX...
LAT...LON 45239264 45179212 44759158 44129127 43789128 43749147
43859200 44009249 44389291 45159302 45239264SPC 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 | Aitkin, Anoka, Carlton, Chisago, Fillmore, Goodhue and 10 more | 7 hr |
| Jul 28, 11:24 PM CDT | Mesoscale Discussion | SPC | Houston, Wabasha, Winona | 96 min |
| Jul 28, 8:59 PM CDT | Mesoscale Discussion | SPC | Chippewa, Clark, Eau Claire, Jackson, Monroe, Trempealeau | 61 min |
| Jul 28, 9:51 PM CDT | Mesoscale Discussion | SPC | Eau Claire, Jackson, Monroe | 54 min |
| Jul 29, 1:34 AM CDT | Mesoscale Discussion | SPC | Kenosha, Milwaukee, Racine, Rock, Walworth, Waukesha | 86 min |
Nearby
Mesoscale Discussions in Minnesota, 2021Mesoscale 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.