A band of heavy rain developed along a warm front that lifted north through southern and central Minnesota during the afternoon and early evening of August 16. Small low-topped supercells developed within the band and produced numerous tornadoes.
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 MPX wrote it up.
A band of heavy rain developed along a warm front that lifted north through southern and central Minnesota during the afternoon and early evening of August 16. Small low-topped supercells developed within the band and produced numerous tornadoes. In addition, a large circulation was noted in southwest Minnesota during the late evening, early morning hours. This circulation produced isolated severe wind gusts near Redwood Falls, along with flooding as this circulation lasted for several hours in the vicinity.
This was the most widespread and intense rainfall event of the year in Minnesota, with 1-2 inch totals covering approximately 50,000 square miles, or about 60% of the state. Totals of greater than three inches were concentrated in a multi-county area in western and central Minnesota, generally centered on the Minnesota River. The largest official 24-hour rainfall report came from Redwood Falls, where the airport recorded 9.45 inches, and a volunteer with the National Weather Service's cooperative observer program reported 8.12 inches.
The flood waters caused significant damage to county and township roads, a section of regional railway, and county agricultural drainage systems. The cost of the damage was estimated at $675,750 in total relief.
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 Twin Cities, MN wrote its last area forecast discussion before the first event at Aug 16, 5:47 AM CST, 13 minutes earlier.
Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 647 AM CDT Wed Aug 16 2017 .UPDATE... Issued at 634 AM CDT Wed Aug 16 2017 Updated to include 12z aviation discussion below. && .SHORT TERM...(Today and tonight) Issued at 350 AM CDT Wed Aug 16 2017 Surface analysis early this morning shows a low pressure center over northwest Kansas/southwest Nebraska with a warm front extending nearly due east to southern Ohio and a trailing cold front extending southwest through the TX/OK Panhandles into central New Mexico. Aloft, the Upper Mississippi River Valley is caught between a ridge axis extending south southeast from western Hudson Bay into the southeast CONUS and a longwave trough over the lee of the Rockies. A poignant shortwave axis curls from west- central Saskatchewan province into eastern North Dakota then into eastern Wyoming. In advance of the surface features, the deep southwesterly flow aloft is tapping moisture from the subtropical jet, pushing PWATs to between 1.50-2.00 inches over the WFO MPX coverage area this morning. A band of light-moderate showers associated with a smaller shortwave aloft will continue to push northeast through eastern MN into western WI. These showers will be only the beginning of what will be a rather wet 30 hours over the coverage area. The larger trough axis aloft will help drag the surface low east northeast, taking a path that will bring it to near KFSD by midday today then over far southern MN tonight to around KMSP by daybreak Thursday morning. This is a slower progression than models have depicted in previous days so have adjusted the precip chances as such. After the showers this morning, there will be a relative break in the action for eastern MN into western WI through early afternoon while western MN sees an increase in rain coverage in advance of the surface low. In the meantime, the trough features to the west will pivot and allow a cutoff low to develop within in, offset to the west of the surface low. As this scenario develops, precipitation coverage should increase steadily this afternoon through this evening, with rainfall potentially heavy at times over central MN. With the deep moisture remaining in place as the surface low moves across, rainfall totals of 1-2" will be commonplace with amounts as high as 3" not unreasonable. Given the recent rainfall over portions of western and central MN recently, isolated flooding issues are possible but the progressive nature of the storm system is not expected to be conducive to training storms. There is also a small risk of severe storms given the enhanced jetting but instability will be meager at best and with little insolation expected and warm sectoring to remain to the south of the area, the risk for severe weather is quite low. The threat for heavy rain will continue into tonight with the slow progression of the surface low but rain coverage and intensity is expected to diminish during the early morning hours into daybreak Thursday. As for temperatures, have continued the trend of advertising slightly cooler temperatures from the previous forecast. As such, will look for highs in the lower 70s in central MN and in the mid 70s in southern MN into western WI. Lows tonight will be similar to this morning, ranging from the upper 50s to mid 60s. .LONG TERM...(Thursday through Tuesday) Issued at 350 AM CDT Wed Aug 16 2017 The longer term concerns remain timing of the exit of the upper trough Thursday. Then timing of the next short wave through the eastern CONUS trough will occur Friday with the next frontal passage for late in the weekend/early next week. The trough exits to the east of the area through Thursday afternoon. Will taper PoPs and overall thunder chances from west to east. Temperatures should remain on the cool side with ample cloud cover remaining over much of the area through late afternoon. The deterministic models trend another short wave moving through the area Friday/Friday night with attendant weak instability. We should see some drier conditions through Saturday and into Sunday across the region as flow aloft becomes more zonal with slowly rising heights. This should allow warmer temperatures ahead of the next frontal system which is progged to move across the area Sunday night through Monday night. Temperatures are expected to warm through the lower and mid 80s through the weekend with increasing dewpoints ahead of the front. Passage of the front could produce locally heavy rain, especially if it moves slower than progged. Severe weather threat is possible be as the front moves through Monday/Monday night as well. Drier and somewhat cooler conditions will develop in the wake of the front through midweek. && .AVIATION...(For the 12Z TAFS through 12Z Thursday morning) Issued at 634 AM CDT Wed Aug 16 2017 Scattered showers with ceilings in the MVFR-IFR range over mainly the MN TAF sites while additional showers drift NE in WI but ceilings are remaining in VFR range. After this small batch of rain shifts off to the NE, we'll look for a break in the action late morning into early afternoon before the atmosphere reloads and a more widespread swath of rain with increased intensity moves in from the southwest. After a combination of MVFR-VFR conditions this afternoon ahead of the additional rain, conditions will likely drop to MVFR late this afternoon then to IFR tonight as the low pressure center shifts ENE over southern MN. Thunderstorms and heavy also possible late this afternoon and evening. The rain will persist through the early morning hours then slowly diminish but ceilings will likely remain within IFR (if not lower) levels. KMSP...Ceilings look to bounce between VFR and IFR for the first couple hours, particularly with small batches of -SHRA moving through the area. Conditions look to remain VFR through late afternoon then drop into MVFR-IFR with the arrival of the showers and thunderstorms later today. Winds will also be tricky later today through tonight as the exact track of the low will determine wind directions, despite them dropping off to around 5 knots. Would be not be surprised to see some variability in direction later this afternoon and evening. /OUTLOOK FOR KMSP/ Fri...VFR. Chance afternoon/evening TSRA. Wind W 5 kts. Sat...VFR. Wind W 5 kts. Sun...VFR. Chance afternoon/evening TSRA. Wind S 5-10 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. && UPDATE...JPC SHORT TERM...JPC LONG TERM...DWE AVIATION...JPC
Hazardous Weather Outlook National Weather Service Twin Cities/Chanhassen MN 352 AM CDT Wed Aug 16 2017 MNZ041>045-047>070-073>078-082>085-091>093-WIZ014>016-023>028- 170900- Douglas-Todd-Morrison-Mille Lacs-Kanabec-Stevens-Pope-Stearns- Benton-Sherburne-Isanti-Chisago-Lac Qui Parle-Swift-Chippewa- Kandiyohi-Meeker-Wright-Hennepin-Anoka-Ramsey-Washington- Yellow Medicine-Renville-McLeod-Sibley-Carver-Scott-Dakota- Redwood-Brown-Nicollet-Le Sueur-Rice-Goodhue-Watonwan-Blue Earth- Waseca-Steele-Martin-Faribault-Freeborn-Polk-Barron-Rusk- St. Croix-Pierce-Dunn-Pepin-Eau Claire- 352 AM CDT Wed Aug 16 2017 This Hazardous Weather Outlook is for portions of central and southern Minnesota...and west central Wisconsin. .DAY ONE...Today and Tonight Showers and thunderstorms can be expected today and tonight. There is a Marginal Risk for severe thunderstorms over southern and southeastern Minnesota into a portion of west central Wisconsin through tonight. The main hazards are large hail and damaging winds. In addition, thunderstorms during this time may contain heavy rain which could cause localized flooding. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday Isolated to scattered thunderstorms are possible Thursday mainly across eastern Minnesota into western Wisconsin. Severe weather is not expected. The chance for thunderstorms increases again Friday afternoon into Friday evening and then again Sunday into Monday night. The severe weather is low at this time. .SPOTTER INFORMATION STATEMENT... SKYWARN spotter activation will not be needed.
The Minneapolis radar (KMPX), 124 km away, was scanning. The volume nearest the first event began at 12:01 UTC.
13 tornado, 7 heavy rain, 3 flash flood, 3 thunderstorm wind, 1 funnel cloud. Local standard time, as filed.
The Redwood Falls airport ASOS measured 9.45 inches of rainfall in 24 hours.
A Department of National Resources rain gauge measured 8.57 inches in 24 hours.
A tornado developed south of Nicollet and moved north-northwest. It caused mainly tree damage, but did hit a farmstead and damaged a garage and grove of trees. Placement of tornado track was based on high-res satellite imagery.
A local observer reported 5.65 inches of rainfall in a 12 hour period.
Shortly after one tornado, a second tornado developed south of Nicollet and moved north. It was observed by a local citizen, and a damage survey showed that it caused damage to corn fields. Placement of tornado track was based on high-res satellite imagery.
A spotter reported two tornadoes near New Sweden. This tornado was confirmed by viewing high-res satellite imagery. Corn fields were damaged.
The strongest tornado of the day developed in northern Nicollet County and lifted into|Sibley County. This was a multi-vortex tornado. Video shows one vortex struck a farmstead directly causing significant damage to trees and out buildings.
The strongest tornado of the day developed in northern Nicollet county and lifted into|Sibley county. This was a multi-vortex tornado. Video shows one vortex struck a farmstead directly causing significant damage to trees and out buildings.
A measured rainfall report indicated 6.49 inches fell near Beaver Falls in a 12 hour period.
A tornado moved across corn fields. It was recorded on video by a storm chaser. Placement of tornado track was based on video and high-res satellite imagery.
A tornado developed east-northeast of Winthrop and tracked toward the west-northwest. It flattened some corn, uprooted trees, and caused other tree damage. Near the end of its path, it destroyed a structurally compromised barn. The maximum wind speed is estimated to have been 80 mph. Most of the path was determined through a combination of NWS storm survey and reviewing high-res satellite imagery.
The COOP Observer for Redwood Falls, Minnesota, measured 8.12 inches of rainfall in a 12 hour period. The 8.12 rainfall total is the new state rainfall record for the date (which was officially recorded the morning of August 17th).
A measured rainfall report indicated 6.82 inches fell near Morton, Minnesota.
A measured rainfall report indicated 6.07 inches fell near Maynard, Minnesota.
A weak circulation developed south of New Prague and moved across the far southwest and western part of town, into Scott County. There was minor tree damage which matched up with radar.
A weak circulation developed south of New Prague and moved across the western part of town, into Scott County, where it knocked over a tree in a cemetery on the west side of town. Just northwest of New Prague, a farm sustained minor damage to trees and outbuildings, along with a chimney that was blown over.
A storm chaser filmed a separate funnel cloud prior to a tornado at 1821 CST. The funnel might have touched down, but it was not possible to determine this.
A storm chaser provided video of a brief tornado that moved across some fields before it dissipated. No crop damage was noted.
A tornado developed near the intersection of 145th Street NW and Mystic Lake Drive. It tracked 1.2 miles northwest. Fencing and tents were blown over, trees were uprooted, and a fish house was spun around. The maximum estimated wind speed was 70 mph.
A brief EF0 tornado between Hutchinson and Biscay. It tracked through corn fields and damaged a few trees.
A brief EF0 tornado on the south side of Lester Prairie produced a concentrated area of tree damage as it headed west. A funnel cloud was observed a few minutes earlier on the east side of town. Estimated max wind speed 75 mph.
Several cars were stalled due to a flooded roadway at the intersection of Highway 101, and Marshall Road in Shakopee.
Trees and power lines were blown down in Redwood Falls.
A report from social media indicated that several trees were blown down in the town of Franklin.
Very heavy rainfall, and associated flooding led to numerous reports of basement flooding in Redwood Falls, and surrounding communities. Flood waters caused damage to roads and drainage systems.
Very heavy rainfall, and associated flooding, led to temporarily closures of Anderson Lake County Park in Franklin, along with Beaver Falls and Birth Coulee County Parks in Morton. Mack Lake County Park in Fairfax, Skalbekken County Park in Sacred Heart and Vicksburg Park in Renville were also closed due to the flooding. Several county roads in southwest Renville County were closed, and some became impassable.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Minnesota in 2017Every state in 2017This day in weather historyThe tornado archive for Minnesota, 2017Warnings in Minnesota, August 2017
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: 717677, 717678, 708106, 720196, 708109, 713493, 708111, 708112, 717673, 713497, 708102, 717674, 717675, 717676, 708114, 713275, 717769, 717768, 708104, 713496, 708105, 717671, 717683, 717682, 717762, 717680, 717681.