The earliest breakup on record has begun in the middle Kuskokwim River, but ice is still holding in the upper and lower sections of the river, according to a story from KYUK Public Media. Those are the results from an aerial survey by the National Oceanic and Atmospheric Administration, which photographed the Kuksokwim from the Holitna River tributary to Napakiak on Monday.

Crane Johnson, National Weather Service hydrologist, says the crew observed in-place sheet ice upstream of the Holitna with some large, open areas.

He says the ice sheet at Sleetmute has shifted. The river from Red Devil to 15 miles upstream of Napaimute has in-place sheet ice that's starting to weaken.

Open water begins just upstream of Napaimute to just upstream of Aniak with ice clinging to the banks. Then, Johnson says, chunk ice and small pans have formed an ice jam around Aniak.

"Then it was sheet ice from Aniak all the way down to the Kuskoquak with some open areas and some shifting but mostly sheet ice that was beginning to weaken," Johnson said. "And then downstream from the Kuskoquak it was in place ice with larger open areas, and the ice was darker and it weakened more."

Johnson says it's typical during a thermal breakup, or mushout as it's also called, for breakup to occur at multiple points along the river. That's different from typical breakups where a main ice front moves downstream.

"The important thing right now is those areas that have open water at Napaimute and Chuathbaluk, they'll see heavy runs of ice as the upriver continues to break up," he said.

Which means, boaters, watch out.

Johnson says Wednesday the National Weather Service will dispatch its annual River Watch team to Aniak. The crew will spend a few days flying the river, sending ice reports to communities and stopping in various villages to help residents prepare for potential flooding. Johnson says it's a precaution, since a mushout reduces the likelihood of flooding occurring.

According to NWS archives, the earliest breakup on record for Aniak since 1957 occurred April 24, 1998. The earliest breakup on record for Kalskag since 1938 occurred April 22, 1940. And the earliest breakup on record for Crooked Creek since 1938 occurred April 13, 1960.

Official breakup dates for communities with open water along the middle Kuskokwim have not been designated. David Streubel, NWS hydrologist, says the river's main ice front moving past communities usually classifies breakup. With the mushout changing that definition, Streubel says the River Watch team will consult with these communities on their selected breakup date.

You can view aerial pictures from the NOAA flight here.