The National Weather Service Climate Prediction Center recently announced a La Niña watch. If their prediction holds up, the Pacific Northwest could see more rain this fall and winter — and maybe some relief from the region’s stubborn drought conditions.
La Niña is part of the El Niño Southern Oscillation, or ENSO, cycle. It refers to a period when lower ocean surface temperatures in the tropical Pacific bring higher precipitation and cooler weather to the Pacific Northwest.
But long-term forecasts remain uncertain. Right now, the Pacific Northwest is in a period called ENSO neutral, meaning weather conditions are somewhere between La Niña and El Niño, its warmer, drier counterpart.
If the right conditions for La Niña persist, the NWS will issue a La Niña advisory, a more stable prediction of cooler, wetter weather for the late fall and winter.
That could be good news for the region.
Larry O’Neill, the Oregon state climatologist, said La Niña could aid in drought recovery.
“One thing that we’re struggling with right now is that we’ve had one of the driest springs and early summers on record in Oregon and Washington,” O’Neill said.
So far this year, Gov. Tina Kotek has declared seven drought emergencies, including two more recently in Coos and Wheeler counties. As part of the declaration, the governor issued an executive order to deliver aid.
“La Niñas are often good for basically ending the droughts or reducing the severity and impact,” O’Neill said.
O’Neill also said that by increasing available water supply, La Niña could relieve some of the strains placed by drought on agriculture and livestock.
The weather pattern could also lessen the impact of drought on fire conditions — but that’s a bit more complicated.
Consider snowpack, for example. By bringing more rain and lower temperatures, La Niña can lead to a greater buildup of snow at higher elevations.
That sounds good for mitigating fire conditions on the ground. But, according to NWS meteorologist Daniel Hartsock, higher snowpack doesn’t necessarily make fires less likely.
“The rainfall that we receive and snowpack over the winter, it doesn’t have a lot to do with the following fire season,” Hartsock said. “It’s more of how much rain, how many rain events, do we get in May and June.”
According to John Saltenberger, the fire program manager at the Northwest Interagency Coordination Center, higher snowpack might slow the arrival of the fire season. But he emphasized that daily weather forecasts have a much greater effect on fire conditions.
Dry summer weather can still lead to more fires even if the preceding winter and spring were wetter than normal, like during La Niña. In fact, the excess vegetation that grows during a particularly wet season can become extra fuel for fires during the dry season.
But even in places where burn scars have stripped the land of vegetation, heavy rain events — like atmospheric rivers and storms — can still be a problem when they hit bare earth. Saltenberger said mudslides and debris flows “create [a] rapid sloughing off of the soil and potentially hazardous circumstances.”
That creates further problems for transportation.
For example, a mudslide could cause a highway closure, leading to interstate congestion. And even in more urban areas, the cool, wet weather makes ice storms and lowland snow more likely, straining transportation and road infrastructure.
Hartsock said the NWS is currently predicting a weak or moderate La Niña winter. But he also said people shouldn’t drop their guard.
“We want to be prepared for anything that could happen,” Hartsock said.
The NWS said it updates the La Niña watch — and could issue a La Niña advisory — on the second Thursday of each month on its ENSO discussion page.
This story comes to you from the Northwest News Network, a collaboration between public media organizations in Oregon and Washington.