Odds are high that the Pacific Northwest will be warmer than average the next three months, and current drought conditions are expected to persist, National Oceanic and Atmospheric Administration scientists said Dec. 20.
Temperatures in Oregon, Washington and Northern California have been generally above average recently. That trend is expected to continue in January, February and March as an El Nino forms, according to NOAA.
“Western snowpack is generally behind average, particularly the farther west you go,” NOAA climate scientist Deke Arndt said. “The Cascades have quite a bit less snow on them than is typical.”
NOAA updated its seasonal outlook for U.S. temperatures and precipitation. More than anywhere else in the Lower 48, the odds favor above-normal temperatures in Western Oregon and Western Washington, according to NOAA. Odds in the rest of the West also lean toward higher-than-usual temperatures.
The odds favor a drier-than-average winter in Oregon, Washington, Northern California and the Idaho Panhandle, with the rest of the West having equal chances of wet, dry or average precipitation.
Nearly 90 percent of Oregon and nearly 33 percent of Washington were in some stage of drought, the U.S. Drought Monitor reported Dec. 20.
“Persistence (of drought conditions) is forecast for the Pacific Northwest,” NOAA meteorologist Brad Pugh said. “That’s related to the low snowpack currently over the Cascades and also the seasonal outlook for drier than normal conditions.”
In Oregon and Washington, snowpacks in the Cascades ranged Dec. 20 from 95 percent of normal near the Canadian border to 39 percent in northern Oregon, according to the Natural Resources Conservation Service.
Pugh said an El Nino has yet to influence the weather. Sea-surface temperatures have been above average for several weeks, but the warm ocean has yet to link up with the atmosphere to form an El Nino. “We haven’t seen that atmospheric response to the warmer than normal sea-surface temperatures,” he said.
Climatologists pegged the chances that a weak to moderate El Nino will form in the next month at 90 percent. An El Nino typically will have its greatest effect on Northwest winters after Jan. 1.
El Nino’s warm waters are along the equator. According to the Office of the Washington State Climatologist, sea-surface temperatures in the Gulf of Alaska also are higher than average and resemble the mass of warm winter that contributed to the 2015 drought. Pugh said those warm waters did not factor into his forecast.
In a conference call with reporters, Arndt said global temperatures for the year will be the among the warmest, according to records that go back 139 years. “It is virtually certain that 2018 will go down in the record books as the fourth-warmest year,” he said.
Through November, 2018 has been the 16th warmest on record in the U.S., according to NOAA. November was cooler and wetter than average in the U.S., even though the West Coast was warm. California had its 10th warmest November on record, according to NOAA.