SALEM — A strong El Nino has a two out of three chance of forming by this winter, the National Weather Service said Thursday, Aug. 10, creating conditions that could lead to a smaller snowpack in the Northwest.

The forecast largely confirmed last month’s outlook, but forecasters said they’re more confident in their prediction. Besides being a month closer to winter, the mid-Pacific Ocean has continued to warm.

Sea-surface temperature in July went from warm enough to trigger a “weak” El Nino to warm enough to ignite a “moderate” El Nino. El Ninos typically get stronger in the fall and peak in the winter.

How strong will it be?

Oregon State Climatologist Larry O’Neill agreed an El Nino was likely and that the outlook favored a warm and dry winter. He said, however, he was hesitant to “go all in” on predicting a strong El Nino.

The atmosphere has been slow to respond to the warming ocean, he said. Thunderstorms over the east-central Pacific that would signal the coming of a strong El Nino have yet to materialize.

“It is something to watch out for,” O’Neill said. “We need to see a stronger atmospheric response.”

Abnormally warm water in the Gulf of Alaska also may make the winter mild, he said.

Storms in September and October may break up the blob of warm water, but current conditions resemble 2014, O’Neill said, when the warm water persisted and the Northwest suffered a snowpack drought.

Drought covers most of Washington and Oregon, according to the U.S. Drought Monitor. An El Nino winter could worsen water deficits that carry into the fall, Washington State Climatologist Nick Bond said.

“All in all, we think this one is going to make a difference,” he said.

An El Nino influences weather worldwide. It could worsen drought in parts of Africa and Asia. It, however, could relieve drought in the southern tier of the U.S.

“A strong El Nino does not necessarily equate to strong El Nino impacts locally,” the climate center said in a statement. “The odds of related climate anomalies (are) often lower than the chances of El Nino itself.”

Forecasters predicted a 66% chance that sea-surface temperatures by November will be 1.5 degrees Celsius or more above normal, warm enough to trigger a strong El Nino.

It’s almost certain the El Nino will be at least moderate, according to forecasters, who have ruled out a fourth straight La Nina.

The last El Nino was 2019, and it stayed weak. The winter of 2015-16, the most recent strong El Nino, was Oregon’s 14th wettest and 43rd warmest and Washington’s eighth wettest and 11th warmest in 129 years of record-keeping.

Climatologists see chance of ‘historically strong’ El Nino

El Nino here, but not yet a big climate force in Northwest