A complex of storms moved across southwest Wisconsin during the evening of August 27th. The storms blew down trees north of Brodtville (Grant County) and power lines in Patch Grove (Grant County).
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS ARX wrote it up.
A complex of storms moved across southwest Wisconsin during the evening of August 27th. The storms blew down trees north of Brodtville (Grant County) and power lines in Patch Grove (Grant County). Funnel clouds were also sighted between in the vicinity of Mount Hope (Grant County).
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS La Crosse, WI wrote its last area forecast discussion before the first event at Aug 27, 5:32 PM CST, 2 hours 12 minutes earlier.
Area Forecast Discussion National Weather Service La Crosse WI 632 PM CDT Fri Aug 27 2021 .SHORT TERM...(This evening through Saturday night) Issued at 245 PM CDT Fri Aug 27 2021 Widespread heavy rain fell west of the Mississippi River last night, particularly south of I-90 where amounts ranged as high as 3 to 5 inches. Another stripe of heavy rainfall fell just north of the I-94 corridor in central Wisconsin with 2 to 4 inches reported. These areas are thoroughly saturated and won't be able to handle any heavy rainfall rates in the short term. With that said, we are monitoring yet another conditional threat for another round of convection to develop late this afternoon into the evening. This next potential round of convection tonight will be highly dependent on the how far north a warm front to our south will make it. The front currently sits right along our southern border per 1 PM surface obs. Widespread cloud cover and rain so far today have really hindered northward progression of the front. That said, clouds have finally managed to thin to some extent along and south of the IA/MN border eastward. Daytime heating down there will prove somewhat favorable for bringing the front a bit northward, but the question remains whether the front gets any momentum from warm advection as models have been so keen to suggest all day. Consensus has stubbornly held to pushing the front north of the I-90 corridor by late afternoon. This would bring favorable CAPE (>2500 J/kg) all the way to the I-94 corridor per HREF. Bringing the front and instability that far north, CAMs then want to initiate another broken line of convection from south-central MN to northwest WI by early evening, which would then propagate southeast through our area. Based on latest trends, confidence is rather low in this coming to fruition. Thinking the front probably won't quite make it to the I- 90 corridor, so then the question becomes whether additional convection initiates over our forecast area, or whether it struggles to develop at all. Severe/flood threat tonight will be highly conditional on whether storms indeed initiate and how much instability they have at their disposal. Instability pool of >2000 J/kg seems likely at least across our far south, but most favorable deep shear resides across our north. There is a healthy amount of shear in the low to mid levels with pronounced clockwise curvature in hodographs this evening. If storms develop and intensify in this environment, could perhaps see a few supercells, possibly a brief tornado. Otherwise the main threats will be localized damaging winds and heavy rain. Pondered the need for a flash flood watch, but decided to hold off due to low confidence and will instead let evening shift monitor trends. According to the convective allowing models, overnight precipitation is expected to exit southeast by the morning hours. Similar to previous forecasts, the exit timing of this activity strongly influences any convection during the daytime hours. A later exit would result in decreased availability for daytime heating and therefore less convection. Mixing out from H850 tomorrow provides maximum temperatures in the high 80s which is again dependent on how much lingering of overnight precipitation and resultant diurnal heating budget. Expect another round of convection during tomorrow night with an amplified transitioning upper-level trough across the upper plains. Ahead of this trough, an associated surface low is expected to track from central NE through eastern SD and central MN. Convective allowing models have been in "closer" agreement regarding this round of convection than previous days activity with initial convection along a frontal boundary from eastern SD to north-central MN near 2000Z. CAMs place the earliest timing for our area near 0100Z. The most favorable region for ascent for our CWA is near 10Z with the equatorward entrance region of the jet maxima downstream of the trough axis overhead. According to the RAP, the strongest southwesterly low-level (H850) prefrontal moisture transport occurs from 0600-1400Z with PWs ~1.8 inches and moisture transport vectors >250 gm/kg. As for severity, the primary cape axis diminishes with the loss of daytime heating whilst remaining to our west. Assuming the storms fire off the boundary and can remain surface based, 0-3km shear values remain substantial(?). In summary, the axis of convection fires off the boundary from eastern SD to central MN in afternoon hours with a southwest to northeast orientation. The motion/propagation of convection follows the synoptic region for ascent to the northeast ahead of a transitioning upper-level trough. While moisture transport seems pronounced, it is likely the main convergence axis remains to our north. It will be prudent to keep an eye on any development as we get closer. .LONG TERM...(Saturday night through Friday) Issued at 245 PM CDT Fri Aug 27 2021 Water vapor satellite today shows a long wave trough over the Canadian Rockies extending south into the northern Rockies of Montana and Idaho. As this feature lifts to the east/northeast through the weekend, it will be the focus for additional rounds of showers and storms. With the round it kicks off Saturday night, there is a decent signal in the models that what remains of this may lift by to the north of the area by early Sunday morning. This is based on the idea that the upper level trough will be either coming across with a positive tilt or at most a neutral tilt. With the strongest embedded short wave trough expected to be north of the area, this would take the best forcing along the the surface low and strongest low level moisture transport north of the area as well. Confidence in this overall scenario is not super high as a couple models do suggest the system could be taking on a negative tilt which would bring stronger forcing to the area and the prospects for more widespread rainfall. The ingredients for heavy rain will still be in place ahead of the cold front Sunday morning where there will be an axis of precipitable waters near 2 inches, the weakening low level moisture transport with warm cloud depths of 3 to 3.5 km. At this point, can only watch what happens tonight and again Saturday to see how this will impact the outcome for Sunday. Once this system moves through, some weak upper level ridging will be in place to provide at least one dry day Monday. However, the front that goes through Sunday looks like it will stall not too far to the south and then get drawn back north into the area ahead of the next incoming short wave trough for more rain chances Monday night into Tuesday. The 27.00Z ECMWF suggest some potential for another heavy rain threat with precipitable water levels returning to around 1.5 inches along and south of the boundary along with an increase in the warm cloud depths to around 3.5 km. As of now, the low level moisture transport axis looks to not be very strong and primarily focused west of the area in the Missouri River Valley. After that, a lot of what happens will depend on the track of Ida. Right now the general idea is that ridging will build over the western U.S. during the middle of the week and should push Ida off the northeast through the Appalachians. This ridging is expected to also build over the Midwest and should give generally dry days for the middle of the week before the possibility of a short wave trough topping the ridge with some more rain chances moving in for Thursday. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 632 PM CDT Fri Aug 27 2021 Showers and storms are likely into tonight with associated potential visibility and ceiling impacts. Will add in tempo MVFR to potentially IFR visibilities/ceilings if confidence increases for storms to directly impact the airports. Current storms are popping up across southeast Minnesota and northeast Iowa. They will continue an east/northeast progression through the region this evening. Storm chances begin to diminish after 06z. There is a potential LLWS threat at KLSE around 09z, but the threat seems marginal at best and was not confident enough to include in the TAF at this time. Winds will be from the south overnight into tomorrow with gusts up to 20 knots by late tomorrow morning. && .HYDROLOGY... Issued at 245 PM CDT Fri Aug 27 2021 Runoff from the rain Thursday night and this morning has resulted in enough runoff from river rises on some the tributaries with a couple expected to reach minor flood stage. As of now, the expected QPF tonight is generally expected to be under an inch, but could fall on the Black River basin which is already saturated and take much additional water. Looking forward to Saturday night and Sunday, the highest rainfall amounts are currently expected to remain off to the northwest of the area, so the additional rainfall that does come in may not pose too much of a threat for more flooding. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && SHORT TERM...Kurz/JAR LONG TERM...04 AVIATION...Peters HYDROLOGY...04
Hazardous Weather Outlook National Weather Service La Crosse WI 428 PM CDT Fri Aug 27 2021 IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ017-029- 032>034-041>044-053>055-061-290130- Mitchell-Howard-Winneshiek-Allamakee-Floyd-Chickasaw-Fayette- Clayton-Wabasha-Dodge-Olmsted-Winona-Mower-Fillmore-Houston- Taylor-Clark-Buffalo-Trempealeau-Jackson-La Crosse-Monroe-Juneau- Adams-Vernon-Crawford-Richland-Grant- 428 PM CDT Fri Aug 27 2021 This Hazardous Weather Outlook is for portions of southeast Minnesota...northeast Iowa and southwest into central Wisconsin. .DAY ONE...Today and Tonight Several rounds of storms are expected this afternoon and evening. Some may be severe with strong winds, large hail, heavy rain, and a few tornadoes possible, especially in southeast Minnesota and northeast Iowa. .DAYS TWO THROUGH SEVEN...Saturday through Thursday Storm chances continue Saturday into Saturday night. Isolated severe storms are possible. The main threats will be locally heavy rain and damaging winds. If the storms repeat across the same areas, flooding will continue to be a concern. .SPOTTER INFORMATION STATEMENT... Spotters may be needed today into this evening and Saturday evening. .EMERGENCY MANAGEMENT COORDINATION... No webinar is scheduled. KDS
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
713 PM CDT FRI AUG 27 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0637 PM FUNNEL CLOUD 5 SSE IONIA 42.97N 92.42W
08/27/2021 CHICKASAW IA PUBLIC
POSSIBLY TOUCHING DOWN, UNSURE.
&&
DBSpecial Weather Statement
National Weather Service La Crosse WI
714 PM CDT Fri Aug 27 2021
MNZ079-087-088-280045-
Wabasha MN-Olmsted MN-Winona MN-
714 PM CDT Fri Aug 27 2021
...Strong thunderstorms will impact portions of northwestern Winona,
central Olmsted and southern Wabasha Counties through 745 PM CDT...
At 714 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from 8 miles southwest of Pepin to Oronoco. Movement
was southeast at 20 mph.
HAZARD...Wind gusts up to 50 mph and half inch hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor damage to outdoor objects is
possible.
Locations impacted include...
Rochester, Plainview, Eyota, Oronoco, Elgin, Marion, Douglas, Viola,
West Albany, Bremen, Millville, Elba, Hammond, Minneiska, Chester,
Beaver, South Troy, County Roads 9 And 10, Rattelsnake Point and
Potsdam.
People attending Soldiers Memorial Field should seek safe shelter
immediately!
This includes Interstate 90 in Minnesota between mile markers 216 and
224.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is also occurring with these storms and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.
A Tornado Watch remains in effect until 1100 PM CDT for southeastern
Minnesota.
&&
LAT...LON 4437 9224 4417 9183 4390 9233 4410 9268
4412 9268
TIME...MOT...LOC 0014Z 305DEG 19KT 4434 9226 4414 9255
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH
SkowPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
719 PM CDT FRI AUG 27 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0648 PM LIGHTNING IONIA 43.04N 92.46W
08/27/2021 CHICKASAW IA LAW ENFORCEMENT
A HOME WAS HIT BY A LIGHTNING STRIKE. TIME
APPROXIMATED.
&&
04PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
743 PM CDT FRI AUG 27 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0742 PM TSTM WND DMG POSTVILLE 43.08N 91.57W
08/27/2021 ALLAMAKEE IA TRAINED SPOTTER
POWER LINES DOWN.
&&
EADPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
751 PM CDT FRI AUG 27 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0655 PM TSTM WND DMG SPILLVILLE 43.20N 91.95W
08/27/2021 WINNESHIEK IA LAW ENFORCEMENT
LOTS OF POWER OUTAGES ACROSS THE SOUTHERN
PART OF THE COUNTY FROM WINDS CAUSING DOWNED
POWER LINES TO LIGHTNING STRIKES.
COMMUNITIES IMPACTED INCLUDE SPILLVILLE,
FORT ATKINSON, OSSIAN AND CALMAR. HEAVY RAIN
ALSO CREATED LOTS OF STANDING WATER IN
CALMAR.
&&
04PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
809 PM CDT FRI AUG 27 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0807 PM TSTM WND DMG MONONA 43.05N 91.39W
08/27/2021 CLAYTON IA FIRE DEPT/RESCUE
REPORT OF POWERLINES DOWN.
&&
EADThe La Crosse radar (KARX), 93 km away, was scanning. The volume nearest the first event began at 01:42 UTC.
4 flood, 3 thunderstorm wind, 1 funnel cloud, 1 flash flood. Local standard time, as filed.
A tree was blown down near the Crawford County line north of Brodtville.
Power lines were blown down in Patch Grove.
A couple of funnel clouds were sighted between Mount Hope and Mount Ida along U.S. Highway 18.
Trees and power lines were blown down along State Highway 56 near Liberty.
Runoff from heavy rains caused several roads to be damaged by water and mud slides.
Runoff from heavy rains pushed the Kickapoo River out of its banks in Readstown. The river crested almost two feet above the flood stage at 12.74 feet on the 28th.
Runoff from heavy rains pushed the Black River out of its banks in Black River Falls. The river crested almost nine feet above the flood stage at 55.93 feet on the 28th. This was the fifth highest crest ever recorded.
Runoff from heavy rains pushed the Black River out of its banks near Galesville. The river crested over three feet above the flood stage at 15.03 feet on the 30th. This was the fifth highest crest ever recorded. The flooding continued into September 2021.
Runoff from heavy rains pushed the Yellow River out of its banks in Necedah. The river crested almost three feet above the flood stage at 17.94 feet on the 31st. The flooding continued into September 2021.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wisconsin in 2021Every state in 2021This day in weather historyWarnings in Wisconsin, August 2021
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 981146, 981148, 981144, 981304, 981165, 981344, 981340, 981341, 981390.