River flooding that began in late August along the Black River near Galesville (Trempealeau County) and the Yellow River in Necedah (Juneau County) ending early in September.
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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.
River flooding that began in late August along the Black River near Galesville (Trempealeau County) and the Yellow River in Necedah (Juneau County) ending early in September.
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 31, 9:40 PM CST, 2 hours 20 minutes earlier.
Area Forecast Discussion National Weather Service La Crosse WI 1040 PM CDT Tue Aug 31 2021 .SHORT TERM...(This evening through Wednesday) Issued at 236 PM CDT Tue Aug 31 2021 Early this afternoon a shortwave trough was passing across eastern Iowa with upstream ridging developing across the northern plains. Most of the associated showers have remained just south of the local area, although some thicker mid/high clouds were impacting northeast Iowa into southwest Wisconsin with A few showers/sprinkles possible through the afternoon. As the wave continues to pass to the southeast, the clouds will decrease late this afternoon with mostly clear skies heading into tonight. Tranquil weather will continue into Wednesday as mid-level ridging gradually builds eastward, while Canadian high pressure centered to the northeast will advect seasonably dry air across the region. Some patchy fog could develop once again tonight in favored valley/low-lying areas. Little change in thermal fields is expected through Wednesday with lows tonight mainly in the upper 40s and 50s and seasonable highs Wednesday in the 70s to low 80s. .LONG TERM...(Wednesday night through Tuesday) Issued at 236 PM CDT Tue Aug 31 2021 The next chance for some rain continues to be centered on Thursday night into Friday. The upper level ridge axis will be retreating off to the east allowing a short wave trough to come out of the Desert Southwest and move across the region. As it does, it looks to start getting ingested into a large upper level low moving across southern Canada, that some of the models are suggesting could cause the wave to start breaking apart and loosing energy. There should still be enough left of the wave to produce at least some weak pv advection in the 500-300 mb layer late Thursday night into Friday morning, with the better forcing going off to the north. This same weakening trend is evident in the low levels as a weak area of low pressure along the incoming cold front looks to dissipate as it approaches the area early Friday morning. However, before it does, there is a decent signal that the activity could produce some locally heavy rains. The instability looks to very low, so most of the activity should just be showers, but there is a good low level moisture transport feed into the region ahead of the short wave trough. Precipitable water amounts should increase into the 1.5 to 1.75 inch range, with the 31.00Z NAEFS indicates is close to 2 standard deviations above normal. With warm cloud depths of 4 to 4.5 km, would expect the showers to be efficient rainfall producers. Fortunately, this system looks to be progressive and with the line coming in oriented north/south the potential for training looks to be rather low, so would not expect this to be much of a flash flooding threat. Once this system clears out of the region, the weather through the upcoming weekend into early next week looks to be rather tranquil. A couple of small chances for some rain with passing systems both Sunday and Monday afternoon. Friday looks to be coolest day with highs mainly in the 60s with seasonable highs mainly in the 70s otherwise. And as a sure sign that fall in approaching, overnight lows look to consistently drop into the 40s and 50s. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1040 PM CDT Tue Aug 31 2021 Cigs: generally skc/sct conditions through the period. Some potential for a few hour window of bkn002 at KLSE, centered around 12z, in response to fog developing in the river valley. This outcome is highly dependent on the low level wind field...with some meso models suggesting they will be too high, while the RAP is trending a bit lighter (favoring low cigs). More on that below... WX/vsby: another clear, light sfc wind night will promote fog in the river valleys. Winds just off the sfc though increase to 10+ kts by 300 ft or so in the NAM/HRRR soundings, holding there through the night. This generally prevents any fog spreading off the river and onto the airport. That said, trends over the past few hours in the RAP is a decrease in these winds overnight...suggesting a greater likelihood of some vsby impacts and associated low cigs. For now, going to lean the forecast toward the low cigs rather than lower vsbys - but as always in these scenarios - which watch trends closely and update as needed. Winds: light easterly through the period, getting a bit more southeast on Thu. && .HYDROLOGY... Issued at 236 PM CDT Tue Aug 31 2021 The flood waters continue to slowly recede with water levels having gone down enough to drop the warnings along the Turkey River. Warnings remain in place along portions of the Black and Yellow Rivers. See the latest flood statements for details. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && SHORT TERM...JM LONG TERM...04 AVIATION...Rieck HYDROLOGY...04
Hazardous Weather Outlook National Weather Service La Crosse WI 340 PM CDT Tue Aug 31 2021 IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ017-029- 032>034-041>044-053>055-061-011100- 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- 340 PM CDT Tue Aug 31 2021 This Hazardous Weather Outlook is for portions of southeast Minnesota...northeast Iowa and southwest into central Wisconsin. .DAY ONE...Tonight No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Wednesday through Monday A few thunderstorms are possible Thursday night into Friday. Organized severe weather is not currently expected. .SPOTTER INFORMATION STATEMENT... No action needed. .EMERGENCY MANAGEMENT COORDINATION... No webinar is scheduled. Rieck
The national radar mosaic for the moment the first event began.
2 flood. Local standard time, as filed.
Flooding that began in late August on the Black River near Galesville ended very early in September.
Flooding that began in late August on the Yellow River in Necedah ended very early in September.
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, September 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: 983645, 983646.