Storm brings floods and snow to Alaska

It is thought that the rainfall was made worst by climate change

Snow buried the high terrain (Getty Images)

A powerful, historic storm has walloped southern Alaska for days, unloading extreme amounts of precipitation and overwhelming its infrastructure in some areas.

The deluge, intensified by climate change, has flooded communities south of Anchorage and transformed trickling waterways into raging rivers. Excessive amounts of snow, measured in feet, have buried the high terrain, and the long-lasting storm won’t fully relent until Wednesday.

The historic rainfall generated by the storm, includes one of the top four heaviest two-day amounts ever observed in the state, nearly 20 inches.

A fire hose of tropical moisture, the remnants of an atmospheric river, instigated the storm system, which will lash California and the Pacific Coast in the days ahead.

“It started on the 29th, that Friday night, and basically persisted since,” said Mike Ottenweller, a meteorologist at the National Weather Service in Anchorage. “It’s still somewhat ongoing.”

The moisture translated to exceptional rainfall in the lowlands, like in the Portage River Valley, where double-digit rainfall totals shattered previous records. Alyeska, Alaska, situated on the Kenai Peninsula where it meets the rest of Alaska, reported 9.53 inches on Halloween – the station’s highest daily total ever recorded.

At the Portage Glacier visitor centre, 10.34 inches was measured 30 October. Its two-day rainfall over the weekend of 18.84 inches ranks as the fourth-highest on record in the state.

“It’s the furthest north location to report consecutive days of 8 inches or more of rain,” said Mr Ottenweller. “The only other place in Alaska that’s done that is Little Port, which is in southeast Alaska. It’s basically a rainforest down there.”

Mr Ottenweller also noted that the 10.34-inch reading marks the first 10-inch day in Alaska since 2010, calling the precipitation totals “more or less unprecedented”. One location had tallied 22 inches by Monday night as the rain continued to come down, which his office referred to as “prodigious”.

“Some of the impacts we had were roads washed out,” Mr Ottenweller said. “We even had a landslide ... basically the side of the mountain just gave way.”

Hardest-hit has been Girdwood, nestled in the Glacier Creek valley about 50 miles south of Anchorage, where the core of the atmospheric river blasted ashore. The quaint former gold mining town, now home to several ski resorts, earned the nickname “Glacier City” for the waterway that runs through its heart. Over the weekend, that quiet creek became a raging, roiling river.

The silty, milky grayish water, fed by glaciers high the Chugach range, carried fallen trees swiftly downstream and swiped precious inches from one neighborhood’s backyard banks. Heavy rains started Friday night. By Sunday, at least a foot of the bank had collapsed.

Early Sunday, a culvert failed, exposing at least six feet of sewer line and a natural gas pipeline. The washout left emergency managers without access to Girdwood’s critical infrastructure, including the wastewater treatment plant, the garbage transfer station and a lot where all the road maintenance equipment is stored.

“Our big hole on Ruane Road was like a new tourist attraction,” joked Michelle Weston, Girdwood’s fire chief. “There were a lot of people coming out in the pouring rain, just to look at the hole.”

Unfortunately for Girdwood, a town heavily dependent on tourism, October is a slow, shoulder season before Alyeska ski resort opens and after summer tourism has long died down.

Toward the south end of town, up a steep hillside, roughly 20 houses stand along Echo Ridge Drive, ground zero for some of the worst impacts to residents. When daylight finally broke Sunday, after two straight days of heavy rain, the road itself looked like a braided stream.

“Next level” is how Alex Roberto described it. She said she had gone to bed with her window cracked “just to listen to the rain.” At 1am, she awoke to the sound of heavy equipment.

“Echo Ridge basically went from a road and turned into a fast-flowing river,” she said. Crews worked all day Sunday to allow residents to access their homes temporarily. Several railroad tracks were also washed out.

The amount of rain that fell on the region not only smashed records, it obliterated them.

“It’s been moderate to heavy rain now for more than 60 consecutive hours,” said Alaska climatologist Rick Thoman. By midday Monday, Mr Thoman, who works for the Alaska Centre for Climate Assessment and Policy in Fairbanks, was using words such as “astounding” and “exciting”.

“What’s remarkable about this is just the absolute amounts of rain and the long duration,” he said.

The exceptional amount of moisture has blasted higher terrain with snowfall. The snow has probably already topped 10 feet above 5,000 feet according to Thoman, with up to several feet more forecast.

The National Weather Service had predicted up to 28 feet on Mount Marcus Baker, a 13,176-foot peak in the Chugach Mountains, about 75 miles east of Anchorage. Mr Thoman said that was almost certainly an overestimate but that there’s no way to know for sure how much snow fell, since there aren’t any mountain gauges that high.

“It’s at a very remote area that’s accessible only by air,” Mr Ottenweller said. “You can only get in there with a chartered aircraft or a private helicopter. Some people do climb that peak, so that’s why the forecast is looked at. It’s kind of like Denali ... totally remote and unexplored.”

At the Portage Glacier visitor center, weather records date back to the early 1970s, but all of the top 10 wettest days on record have occurred since 2001 - a symptom of Alaska’s rapidly warming climate.

As the atmosphere warms, the can hold more water, translating to a greater frequency and intensity of extreme precipitation.

“In a previous climate, maybe this was a one-in-multi-hundred-year event for Girdwood,” Mr Thoman said. “In our warming atmosphere (and) warming oceans, this is still an extreme event, but the chances of this much rain over a few days goes up dramatically, so we like to say that our changing environment increases the chances that we’ll see these kinds of events - and not just in Alaska but around the world.”

The Washington Post