Willow Creek forecast to reach minor flood stage Tuesday under Susitna Valley flood watch

Willow Creek at the Parks Highway is forecast to cross minor flood stage Tuesday morning and peak at 10.29 feet at 4 p.m., the same day as Alaska's Aug. 18 primary.

The National Weather Service in Anchorage issued the flood watch at 12:33 p.m. Sunday for the Western, Southern and Central Susitna Valley, the eighth such watch this year.

It takes effect at 7 p.m. Sunday and runs through 6 p.m. Wednesday, covering Skwentna, Willow, Talkeetna, Trapper Creek and Petersville.

Forecasters expect 2 to 4 inches of rain upstream of the Lake Creek and Yentna rivers and 1 to 2 inches near the Parks Highway from Willow through Talkeetna by Wednesday morning, with light rain continuing through at least midweek. The watch describes flooding as possible, not certain, and says it could develop later in the forecast period.

"Those living in areas prone to flooding should be prepared to take action should flooding develop," wrote forecaster Rux.

The weather service's 5:30 a.m. Sunday forecast discussion linked the rain to an upper level low pushing into Southwest Alaska on Monday, which will turn winds aloft southwesterly into the Susitna and Matanuska valleys. Wet, unsettled conditions are expected to persist across Southcentral Alaska through the end of the week.

The Willow Creek gauge read 6.67 feet at 2:51 p.m.

Sunday, carrying 666 cubic feet per second, well below flood stage. Forecasters expect the creek to reach 8.25 feet by 10 p.m. Monday, passing the 9-foot action stage overnight and crossing the 10-foot minor flood stage by 10 a.m Tuesday.

There it should peak with a flow of 3,930 cubic feet per second, nearly six times Sunday's level.

Johnson Drive and nearby roads become impassable once the creek reaches 10.5 feet, above this week's expected crest.

The Skwentna River is forecast to peak at 39.52 feet Tuesday, below its 40.5-foot action stage and 2.5 feet under minor flood stage. Willow Creek reached 10.78 feet on July 23, and the Skwentna hit 40.47 feet on July 21, both higher than this week's forecast.

July flooding put water in Yentna River lodge cabins and led to a state disaster declaration for Talkeetna on July 25. Federal researchers say extreme precipitation is increasing across Alaska, eroding riverbanks. No gauge forecast exists for the Yentna or Lake Creek, where the heaviest rain is expected.