Weather Alert in Alaska

Flood Warning issued August 12 at 9:58PM AKDT until August 14 at 8:00AM AKDT by NWS Juneau AK

AREAS AFFECTED: City and Borough of Juneau

DESCRIPTION: USGS laser gauge data from Suicide basin indicates a release from the basin is ongoing. Mendenhall lake levels are also showing a release has started. A crest is expected around Wednesday morning to midday with near record levels between 16.25 and 16.75 feet. The reason for the change is crest timing is due to rain masking the start of the sub glacial release and refining the initial start time of the event. * WHAT...Flooding caused by a glacier-dammed lake outburst continues. * WHERE...The Mendenhall Lake and River near areas around the glacier visitor center, the Mendenhall campground, Skaters Cabin Road, View Drive and possibly below Back Loop bridge. * WHEN...Until 800 AM AKDT Thursday. * IMPACTS...Flooding near Mendenhall Lake and River locations is occurring. * ADDITIONAL DETAILS... - At 945 PM AKDT, gauge reports indicated a glacier-dammed lake outburst across the warned area. Flooding is ongoing, especially near the Mendenhall Lake and River. The reason for the change in crest timing is due to rain masking the start of the sub glacial release and refining the initial start time of the event. - The outburst flood forecast is based on an estimated volume of water in the glacier dammed lake and an estimated release rate based on previous events. The extent of water drainage within the basin (partial or full) can vary widely between outburst flood events and is a major source of uncertainty in the forecast, particularly with regard to the peak flood stage. - For Mendenhall Lake : At 9:45pm the stage was 12.76 feet and rising. Flood Stage is 9.0 feet. Forecast: A record crest between 16.25 and 16.75 feet is expected between 8am and Noon Wednesday. Water levels will go above 13 feet around 10 pm Tuesday. Water levels will go above major flood stage early Wednesday morning. Water levels will go below major flood stage around Wednesday night. Impacts: At 11.0 feet: Some homes along View Dr will have up to 1.5 feet of water in yards. Locations below back loop bridge will see bank erosion along unreinforced river banks along with hazardous navigation from debris in the river. Homes along the river on Meander Way will begin to see flooding of some backyards on the outside of the HESCO levee. Portions of the Dredge Lake Trail System will be impassable. Flood waters start to reach Dredge Lake. At 11.5 feet: The low section of road past 9374 View Dr will begin to flood along with water approaching some homes towards the end of road. At 12.0 feet: Significant bank erosion along unreinforced river banks. The low section of road past 9374 View Dr will be flooded with up to 0.5 feet of water. Some houses on the south side and the east end of View Dr will start to flood. Water begins to flood some backyards of homes on the northside of View Dr as well as other low lying areas. Back Loop Rd Bridge will be closed during outburst events. At 12.5 feet: 2 to 4 feet of water in some backyards along Meander Way on the the river side of the HESCO levee. At 13.0 feet: The low section of road past 9374 View Dr will be flooded with 2 ft of water. Water begins to flow through some backyards of homes on the northside of View Dr and flood low lying areas. A few locations on View Dr will see depths of 1 to 2 feet of water in homes. At 13.5 feet: Water starts to back up behind homes between Riverside Dr at Tournure St and Mendenhall River School. Locations on River Rd with low river banks will begin to see water inundate yards. Severe bank erosion along unreinforced river banks. At 14.0 feet: The low section of road past 9374 View Dr will be significantly flooded and impassable. Water will begin to flow over the road from water flowing behind homes on the north side of View Dr. More homes along View Dr will begin to see moderate to major flooding. Locations on River Rd with low river banks will begin to see water approach driveways. At 15.0 feet: Major flooding of multiple homes along View Dr. Water will begin to approach a few homes along River Rd with low river banks with possible flooding of driveways and 1 to 2 feet of water in backyards. Up to 1 foot of water covering Riverside Dr at Tournure St and Mendenhall River School. At 16.0 feet: Water starts to overtop the bank and flood low lying areas near Wildmeadow Ln. Up to 0.5 feet of water will be in the intersection of Skaters Cabin Rd and Arctic Cir. Some backyards of homes between Tamarack Ct and Whitewater Ct will start to see flood waters along with water approaching River Rd near homes with low river banks and possibly flooding those homes. Water will start to flood backyards of homes on Meadow Ln and Stikine St. At 17.0 feet: This is an estimate that water will be overtopping the river banks and flooding into the homes around Wildmeadow Ln. Businesses in the Vintage Park Blvd area will be surrounded and potentially inundated by flood waters. Homes on Meadow Ln from Stikine St to Eagle St will be inundated with flood water. Water will be covering Tournure St from Riverside Dr to Columbia Blvd. Black Wolf Way and Pond Vista Dr will have water across the roads. All parts of View Dr will be covered by flood water.

INSTRUCTION: Please report observed flooding to local emergency services or law enforcement via the Flood Hotline at 500-0890 when you can do so safely. Mariners within Stephens Passage should be advised and exercise caution as numerous trees and and debris have been reported in the river and may have washed downstream. The cold water temperatures can increase the threat of hypothermia and lower the time required to cause hypothermia. Stay tuned to further developments by listening to your local radio, television, or NOAA Weather Radio for further information.

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