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Alaska rivers remain iced up; flood danger still moderate

Jerzy Shedlock

Rivers across Alaska, including the Yukon and Kuskokwim, which flow through or near many towns and villages, remain frozen due to a lingering winter that’s clearly overstayed its welcome. One glance at the National Weather Service’s river forecast map and it’s apparent a frozen and snowed-over landscape still is the norm from the North Slope to as far south as Juneau. Luckily, these cooler springs only occur every two to three decades.

“Even the Southeast, which usually doesn’t have a lot of ice breakup or prolonged snowmelt, (is) carrying snow way later than normal,” said weather service hydrologist David Streubel. “Pretty much everywhere (in Alaska) is experiencing a cold spring. Snow accumulated in April, and the snow and rivers haven’t had many days to melt.”

Along the Kuskokwim River, a 702-mile waterway that cuts through southwestern Alaska, the weather service has forecast a later-than-average breakup -- when warmer temperatures, longer days and melting snow causes ice to break apart and float down Alaska rivers -- at each of its observation points. Near McGrath, population 401, the river generally loses its ice cover on May 7. This year, the river could stay frozen until May 21. Bethel, population 6,219, which is southwest of McGrath, normally sees the river open up on May 12, but this year the ice could remain until May 27.

The Yukon River, more than double the length of the Kuskokwim at 1,980 miles, stretching from British Columbia to Alaska’s western coast, is experiencing the much of the same. Every observation point along the river -- Eagle, Galena, Koyukuk, Marshall and other communities -- has a forecasted breakup later than normal.

Flood potential is moderate for all of those villages. And nearly half of the points along the Kuskokwim River have moderate flood potential, too. In fact, last week, the Weather Service rated the entire state’s flood potential as moderate.

Although the current flooding forecast only raises slight alarms, the ingredients have been set for an eventful breakup. Typically, ice jam floods require cooler-than-average temperatures for most of April, followed by an abrupt transition to summer-like weather in late April to early May. And with May entering its second week, the possibility of temperatures shifting dramatically over the next 10 days is all the more likely.

“If temperatures in the state, especially the Interior, just shift to normal, all that warming ripens the snowpack, pushing a lot of low elevation snow into the river system,” Streubel said. “With the river ice not having a lot of time to melt, it greatly increases not only the probability of ice jams but also the severity that usually goes with those jams that result in flooding.”

But if the warm-up occurrs gradually, he added, Alaska will avoid “a breakup (it) will remember for years.”

Expect breakup to pick up within the next 10 days, he said.

Ice jam flooding inundated Eagle, a speck of a town near the Canadian board, back in 2009. Water levels rose well above the river’s banks, and the town’s historic river front was wiped out. This year, residents are taking precautions; Eagle’s mayor even made personal visits to homeowners closest to the Yukon.

Fairbanks, Alaska’s third largest city, and its surrounding communities, could be affected regardless of ice jams. Snowmelt flooding independent of the ice jams on the Chatanika River, which flows into the Tanana and on to the Yukon and the Salcha River may cause problems. It’s rare, Streubel said, but the current conditions have increased the likelihood.

This year, April temperatures statewide were among the coldest in decades, reported the Weather Service, compared this year’s prolonged winter with its historical database, and found that 1964 may be a similar year. Early April was looking up with warmer temperatures that year, but it didn’t last long, and the rivers didn’t get a chance to thaw. Then, it got cold. And it stayed cold until late May, said climatologist Rick Thoman.

“Certainly, 2013 is a once-every-few-decades kind of spring, as far as persistently low temperatures,” he said. “It’s not completely unprecedented, say outside the realm of what’s happened in the last century, but it’s only happened a handful of times.”

Throughout May of 1964, the highs in Fairbanks and Anchorage were below freezing. The latter had a high of 19 degrees for two consecutive days, May 8 and 9, and the morning of May 9 holds record the latest day with below-zero temperatures in the Interior city. In Anchorage, May 9 had a high of 27 degrees. That’s the latest sub-freezing high on record for Alaska’s largest city, Thoman said.

And 1964 had some “very severe breakup conditions,” with flooding along parts of the Yukon River, Thoman said.

Perhaps the only positive to the season is its effect on the wildfire season. The 2013 wildfire season is off to a sluggish start, and the state isn't likely to burst into flames anytime soon. According to the Alaska Interagency Coordination Center, May has a lower-than-normal fire potential due to Alaska’s stubborn winter.

Jerzy Shedlock can be reached at jerzy(at)alaskadispatch.com