PROJECT ALERT NOTICE (MN) Flooding in Minnesota, day 11

Date: Thu, 20 Apr 2023 17:54:12 EDT

Summary: Flooding from near record snowpack across Minnesota is transitioning to mainstem rivers.

Most tributaries have peaked while mainstem rivers continue to rise including the Red River of the North, Rainy, St Croix, Minnesota, Mississippi Rivers. These mainstem rivers are forecast to begin peaking in the next few days and continue into the following days or weeks. About 0.5 – 1.5 inches of rain fell in southern MN overnight but it seems to have only extended forecast peaks and not raised them substantially.

Currently 38 are above NWS flood stage; with 21 above moderate flood stage and 4 above major flood stage. The NWS forecasts 6 gages will peak above major flood stage during the current forecast period.

One gage in Voyageurs National Park and near the Canadian border stopped telemetering April 18: 05129290 Gold Portage Outlet from Kabetogama Lake near Ray, MN. Unfortunately, the gage cannot be accessed safely for repairs until the ice goes out from Kabetogama Lake.

Today only three staff from Minnesota were in the field making one discharge measurement for a previous rating extension and repairing a gage. Office staff have supported field efforts, communicated with other agencies including the NWS & USACE via NWSChat, responded to emails and phone calls. Since flooding began in earnest April 10, about 100 discharge measurements have been made, 2 stage-discharge ratings have been extended, 2 sites have been flagged for possible indirect measurements, a few sites have lost orifice lines, and many crest-stage pipes have been lost or damaged to ice out. Most peaks to date have estimated Annual Exceedance Probabilities of 0.1 - 0.50. However 05291000 Whetstone River at Big Stone City, SD peak had an AEP <0.01.

News media have been interested in USGS gaging station webcams installed since our last major flood in 2019. NBC-affiliate KARE11 Minneapolis featured a extended (2-3 minute) story about webcams:
https://www.kare11.com/article/news/local/breaking-the-news/network-of-river-cameras-offer-helpful-view-of-flooding-to-the-public-and-experts/89-7e114095-4a81-4fcb-837f-2724d712b476
Other media previously posted USGS time lapse videos ice going out and rivers rising, including the Minneapolis Star Tribune https://video.startribune.com/watch-rivers-rise-rapidly-across-minnesota/600267080/
and Minnesota Public Radio https://www.mprnews.org/story/2023/04/12/river-levels-flooding-forecasts-minnesota-map
Today WCCO CBS affiliate interviewed staff to better understand what stage or gage height refer to. That is scheduled to air tonight.

The 7-day QPF calls for little or no precipitation. This will likely be the last Project Alert unless conditions change.