A number of rivers in Northwest Alaska and parts of the Interior may see flooding amid heavy rains expected to arrive over the region by Friday, according to the National Weather Service.
The weather agency's Fairbanks office issued a special weather statement Wednesday morning covering the coast of the Chukchi Sea and eastern areas of Norton Sound, as well as valleys along the lower and middle Yukon River, the Kobuk and Noatak rivers, and the upper Kuskokwim and lower Koyukuk rivers.
According to meteorologists the rainfall, driven by weather moving east across the Bering Sea from Siberia, could lead to "significant rises in the levels on many rivers and streams," as well as full-blown flooding.
"The greatest potential for flooding will be on rivers and streams draining out of the Brooks Range and in the upper Kobuk and Noatak valleys," meteorologists wrote. "Significant rainfall is expected to begin in the western Brooks Range and in the lower Noatak Valley Friday night and in the upper Kobuk and Noatak valleys Saturday."
Fairbanks-based meteorologist Ed Plumb said Wednesday at least two weather systems were driving the increased rains.
"We've got a pretty active pattern moving into the western and northwest part of the state," Plumb said. "We've got another weather system coming right on the tail of that one off the eastern tail of Russia, moving into the western Chukchi Sea and the northern Bering Sea Friday night into Saturday."
Coastal communities are expected to see pounding surf and storm surges but no flooding, Plumb said, with the first system arriving Friday in eastern Norton Sound affecting villages like Elim, Golovin, Koyuk and Unalakleet. The second, passing through the eastern Chukchi Sea overnight Friday into Saturday, will reach areas north of the Seward Peninsula including Cape Lisburne, Kivalina, Point Hope and Wainwright.
"Even Barrow will see some elevated surf," Plumb said. "The seas are going to get pretty rough — (we're) just suggesting that people move their stuff up the beach a bit."
Plumb said areas northwest of Kotzebue may see the most rainfall, estimated at an inch and a half on Friday alone and several inches over the weekend. He added, however, that forecasters were most closely watching the western Brooks Range.
"Our biggest concern for the rain is in the Brooks Range, because the terrain is steeper and it's more prone to flooding," Plumb said. "In addition, the steep terrain enhances the precipitation — so you can get more rainfall in those mountainous areas."
Areas to the north of the mountains may also see rain from the rising rivers as the systems develop.
"There will be quite a bit of rain on the north side of the Brooks Range; rivers draining onto the North Slope will be (getting rain) so there'll be quite a bit of water there as well," Plumb said.
Crane Johnson, a hydrologist with the weather service's River Forecast Center in Anchorage, said few predictions were available for the extent of water-level increases along the rivers, due to limited river-gauging sites. Most rivers are expected to become "bank-full," or completely fill their channels, with any further rise may lead to flooding — due to the precipitation.
"Bank-full with some flooding possible is sort of the general description (of the forecast)," Johnson said.
Johnson asked people such as Bush pilots planning travel or other activities in the affected regions to keep the rising water levels in mind.
"Just plan ahead — be aware that the water level in that area is going to rise over the weekend and into next week," Johnson said. "One of the issues is that gravel bars that people normally land on or use will be underwater."
Plumb said the systems causing the rain were expected to dissipate early next week.