A forecast of ‘excessive rainfall’ prompts flood watch for much of Southcentral Alaska

homes on a hillside
The Anchorage Hillside on Aug. 25, 2023. (Matt Faubion/Alaska Public Media)

Continuing rains this summer could produce significant flooding in parts of Southcentral Alaska this weekend, as a cool wet streak continues across the region into next week.

The National Weather Service’s Anchorage office issued a flood watch, one step short of a warning, for most of Southcentral from 4 p.m. Friday through Saturday evening.

“Flooding caused by excessive rainfall continues to be possible,” it says.

The watch calls for peak amounts of 2 to 4 inches of rain in mountains north of Turnagain Arm, with 0.7 to 1.5 inches in populated areas such as the Anchorage Bowl, Matanuska Valley and western Kenai Peninsula.

NWS meteorologist Michael Kutz said Friday morning that several Southcentral weather stations ranging from Talkeetna to Portage had recorded more than an inch of rain over the past 24 hours. Koliganek, on the Alaska Peninsula, had already seen nearly 2.5 inches of rain, with 2.2 inches recorded in Cordova.

Kutz credited the scale of the rainfall to the ongoing interplay of a high-pressure and a low-pressure system over the Pacific Ocean, delivering a near-constant deluge to the region this summer.

“It’s basically because of the geographic size of this thing, forcing a lot of the systems to curl up and come through the Gulf of Alaska and ultimately over us here in Southcentral,” he said.

The cool summer has been a boon to wildfire crews across the state, although it’s been more of a cruel summer for peony growers whose cash crops of the flower have suffered under the unusual conditions.

Any flooding that occurs this weekend, according to Kutz, would have its greatest effect in smaller creeks that might overrun their banks. The effects could be compounded along Anchorage’s Campbell and Chester creeks, which pass through paved urban areas less able to absorb floodwaters.

“An inch of rain, over one acre of ground, will produce over 27,000 gallons of water,” Kutz said. “And we have a whole lot of acres over just the plain Anchorage area, much less than the rest of Southcentral Alaska.”

Anchorage’s local forecast calls for a chance of rain every day until at least Thursday. But Kutz said sporadic breaks in the pattern should offer residents some relief.

“Into Sunday, we’ll see a very brief pause, and then we’ll start building back up with the next impulse,” Kutz said. “Basically, if you look at that flow between the high and the low, what we get is little ripples in the system.”

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Chris Klint is a web producer and breaking news reporter at Alaska Public Media. Reach him atcklint@alaskapublic.org.Read more about Chrishere.

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