An erupting Mount Redoubt exploded again at 4:31 this morning -- its fifth and strongest discharge yet -- sending an ash cloud to new heights, the Alaska Volcano Observatory reported.
Ash has now been detected at 60,000 feet above sea level, the National Weather Service reported.
Mid-level winds are still carrying the ash plume north over the Susitna Valley, and minor ash fall has been reported in Skwentna, Willow, Trapper Creek and Talkeetna, according to the Weather Service, the Matanuska-Susitna Borough and eyewitness reports.
High-elevation winds above 40,000 feet are beginning to veer toward Anchorage, but no ash is expected to fall on Alaska's largest city at this time, Bob Hopkins, the meteorologist-in-charge of the National Weather Service office in Anchorage said.
"Eight miles up -- that's going to stay there," Hopkins said. "But that will affect aircraft at that altitude."
It's the lower-elevations winds between 10,000 and 20,000 feet, currently blowing north by northeast, that are most likely to carry ash to the ground, Hopkins said.
In the Su Valley, the ash fall is being described as fine gray dust.
"It's coming down," Rita Jackson, 56, said early this morning at a 24-hour grocery store in Willow. She slid her fingers across the hood of her car through a dusting of ash.
She was taking a sip of coffee when she tasted something funny on her lips, Jackson told The Associated Press. It was ash. She said she then hurried home to get a motorcycle, snowmachine and vehicles under protective blue tarps.
Redoubt began erupting Sunday night, with the first explosion coming at 10:38 p.m., followed by another at 11:02 p.m., a third at 12:14 a.m. and a fourth at 1:39 a.m., the AVO reported.
Ted Stevens Anchorage International Airport remains open, although some airlines have canceled or diverted flights. Alaska Airlines reported canceling 19 flights in and out of Anchorage because of the ash.
Elmendorf Air Force Base reported that 60 planes, including fighter jets, cargo aircraft and a 747 commercial plane, are being sheltered. The base initially ordered only essential personnel to report for duty; that was later changed to all personnel reporting at 8 a.m.
School is in session in Anchorage and the Mat-Su Borough.
Mount Redoubt, a 10,197-foot stratovolcano 100 miles southwest of Anchorage, last erupted during a fourth-month period in 1989-90. Its recent period of volcanic unrest began Jan. 25.
An official with the Federal Aviation Administration at the Anchorage airport early Monday said there were no immediate plans to close the airport.
The Weather Service advised people in areas of ash fall to seal windows and doors, protect electronics and cover air intakes and open water supplies as well as minimize driving.
The AVO staff also warned authorities at the Drift River Oil Terminal -- on the western shore of Cook Inlet downriver from the volcano -- that mud flows and flooding from melting glaciers might be headed their way.
Cook Inlet Pipe Line Co., which operates the terminal, said early this morning that it had begun shutting the facility down.
At a 3 a.m. press conference today, John Powers of AVO said given the hot material landing on snow, mud and snow slides could be expected and staff would check the Drift River area at first light today.
Protective dikes have been constructed at the terminal since Redoubt last erupted nearly 20 years ago..
Powers also said -- looking at the history of Redoubt eruptions -- that this event could be expected to go on for some time, even months.
The eruption has apparently disrupted transmissions from the observatory's webcam inside a hut near the volcano, AVO geophysicist Peter Cervelli said.
For two hours prior to the eruption, AVO scientists reported heightened seismicity at Redoubt and warned there could be a quick escalation to eruptive activity.
The volcano had been on orange "watch" status for most of Sunday after activity began increasing Saturday, but was changed to red after the first eruption.
The Associated Press contributed to this story.
By GEORGE BRYSON