PORTLAND, Ore. (KOIN) — An atmospheric river and strong jet stream are aimed at Oregon and Washington this afternoon bringing heavy rain, damaging winds, and above normal temperatures this weekend.
A high wind warning has been issued for the north Oregon coast and south Washington coast starting at 1pm today until 10pm tonight.
A flood watch is in effect for western Washington and most of western Oregon this afternoon through Sunday night. The Willamette Valley may encounter 1 to 3″ inches of rain, with the focal point of highest rain totals arriving in Salem, as indicated by the latest model runs. The coast, coast range, and Cascade foothills could collect upward of 4 to 5 inches of rain.
As temperatures warm this weekend snow levels will also rise to 7,000 feet. When you pack on 17″ inches of snow in a week, rain falling on top of that snow will result in a loss we would rather see around our waist. It’s also worth noting that because we’re relatively early in the season we don’t have a ton of snow in the Cascades. This will help mitigate snowmelt simply because there is less snow to melt. Current snow bases at Mt. Hood resorts: Timberline – 72″ inches at 6,000 feet. Mt. Hood Meadows – 60″ inches at 5300′.
Learn why atmospheric rivers are a key player in mitigating drought in my interview exactly one year ago with Dr. Andrew Martin, PSU. You can also experience the thrill of tracking an atmospheric river from 40,000 feet onboard a hurricane reconnaissance plane with me.
Rainfall will be most significant from Saturday afternoon to Sunday night.
Add Monday’s rain to weekend totals and you get up to 5″ at the coast and foothills.
A Flood Watch means there is a potential for flooding based on current forecasts. You should monitor later forecasts and be alert for possible flood warnings. Those living in areas prone to flooding should be prepared to take action should flooding develop. Landslides and debris flows are possible during this flood event. People, structures, and roads located below steep slopes, in canyons, and near the mouths of canyons may be at serious risk from rapidly moving landslides.https://forecast.weather.gov/wwamap/wwatxtget.php?cwa=pqr&wwa=flood%20watch
How flooding is exacerbated. Warm temps + rain = snowmelt.
Take a look at the latest model output for precipitation timing by pressing play.
A high wind warning for north Oregon and south Washington coasts will be in effect today at 1pm until 10pm tonight. Southerly winds are forecast to reach a sustained speed of 25 to 40 mph with gusts 50 to 65 mph. At those speeds, expect damage to trees, possible falling trees and power outages.
Gusty south winds are also expected in Portland today.
There is a concern for debris flow in recently burned communities. This map from Inciweb shows the perimeter of areas burned in Oregon September 10, 2020.
Here are a few of the recent flooding events we’ll never forget. One major thing these floods had in common, an atmospheric river and snowmelt.
February 2020 eastern Oregon river flooding
Willamette Valley Flood 1996