PORTLAND — Halfway through May, most major water basins in Oregon continue to have above-average mountain snowpack, though some areas are melting out at a record pace following several weeks of unseasonably warm weather. 

Timing of snowmelt is critical because runoff helps to fill streams for farms and fish. The more snow that melts now, the less will be available later in the summer.

Larry O’Neill, state climatologist, said the area of biggest concern is Central Oregon, which is already mired in severe to extreme drought.

From the Ochoco Mountains east to the Strawberry Range, any snow that had fallen below 6,000 feet of elevation is gone, O’Neill said.

The rate of snowmelt over the last three weeks has been “historically rapid,” he said. 

“May is turning out to be very warm for Oregon,” O’Neill said. “I think this will be a major story in how we transition to summer.”

While snowpack typically peaks on April 1, data from the USDA Natural Resources Conservation Service shows there is still plenty of snow remaining in he mountains for this time of year.

As of May 18, snow-water equivalent — the amount of water contained in snowpack — ranged from 153% of average in the Upper Deschutes Basin to 180% in the Rogue and Umpqua basins; 228% in the Willamette Basin; 258% in the Klamath Basin; and 570% in the Harney Basin. 

How long it sticks around will go a long way toward determining the summer outlook for drought and wildfire potential statewide, O’Neill said. 

“Our research has shown that the fire risk going into August and September is highly dependent on precipitation and temperature in April, May and June, and less so on conditions throughout the full water year,” he said. 

O’Neill highlighted a swath of Central Oregon, including Crook and Jefferson counties and parts of Deschutes County, as the state’s “problem spot” for drought. A combination of high temperatures, evaporation and long-term precipitation deficits are making it difficult for the region to recover, he said. 

“We got some good precipitation this year, but it was not enough to recharge the dry soils,” he said. 

The National Oceanic and Atmospheric Administration’s Climate Prediction Center is calling for a greater chance of above-normal temperatures throughout Oregon over the next three months, meaning snowmelt could continue at a rapid pace. 

Farther west, O’Neill said snowmelt has also been historically fast at several lower elevation monitoring sites in the Cascades.

Still, O’Neill said he expects melt-out on the west side of the Cascades will be slightly later than normal, given just how much snow fell over the winter. 

On the east side of the Cascades, areas around Chemult and Three Creek Meadow have already melted out early, O’Neill said. It is a trend that he expects to continue in the future, further emphasizing the need to build resilience around water supplies. 

“We have to be prepared for prolonged periods of drought,” he said. “The projections show that dry periods will be drier, and wet periods will be about the same as they were. Summer water supply is probably going to decrease as we go forward, overall.”