Pacific Northwest: Atmospheric River to Bring More Rain

25 Sep 2020, 11:00 am

After smoke and wildfires in Washington and Oregon earlier this month, the Northwest finally got some relief earlier this week from an atmospheric river event which brought record breaking rainfall to Seattle Wednesday and Thursday. Additional chances for heavy rain are expected to continue on Friday as a strong trough digs into British Columbia.

Setup

Through the weekend, additional showers will be possible across the Northwest, though most of the moisture will be confined to areas along and west of the Cascades. A few scattered showers and snow flurries could push through the interior Saturday into Sunday morning. A large ridge is expected to build along the West Coast into early next week which will bring warm and dry conditions back to the region.

As of Friday morning, three day rain totals had already surpassed 9 inches in Olympic National Park, while many mountain rain gauges had topped 3-4 inches.

Check out these 3 day rainfall totals! Owl Mt in the Olympics is the winner with close to 10" so far! Detailed list: https://t.co/sdIFNK1vL1 #wawx pic.twitter.com/eUy50YZxfN

— NWS Seattle (@NWSSeattle) September 25, 2020

Forecast

Enough rain could fall on Friday to trigger flash flooding, primarily over the higher terrain and near burn scars. The Weather Prediction Center has issued a marginal risk for flash flooding for the areas highlighted below. In addition, heavy surf and strong winds will lead to dangerous maritime conditions.

The simulated radar images below depict when/where precipitation is expected to occur as the front moves inland Friday into Saturday. The heaviest and most widespread shower activity is expected through Friday afternoon, before the bulk of the rain moves east of the Cascades and becomes more scattered.

By Sunday morning, scattered showers are expected along and west of the Cascades while some heavier precipitation is still expected inland across Idaho, Montana, and Wyoming. Higher elevations could see snow into Saturday morning with another round possible in the Rockies of Montana and Wyoming Saturday night into Sunday.

Additional rain totals through the weekend could still surpass 3-4 inches in some isolated areas while over half a foot of snow could accumulate on the high peaks of the Northern Cascades and in Wyoming’s Northwestern Mountains.

Remember if you encounter flooding in a vehicle, do not try to cross the water. Recent burn areas will be especially susceptible to flash flooding, mudslides, and debris flows.

About the author

Alana Cameron

Alana Cameron was born and raised in Canada in the city of Mississauga, just outside of Toronto. Alana is the oldest of 4 siblings, all close in age, and grew up playing outside with them in all types of weather. After graduating high school, Alana moved to study at the University of British Columbia in Kelowna for a year before transferring to Dalhousie University in Halifax, Nova Scotia where sh... Load Moree completed a Bachelor of Science in Physics and Atmospheric Science. Upon completion, Alana moved back to Toronto where she completed a post-grad degree in Meteorology at York University. After her post-grad, she went on to complete another post-grad in Broadcast Journalism - TV News at Fanshawe College in London, Ontario. During her final year of studies she had the privilege of interning with the best in the business in Canada at The Weather Network. Once she finished her internship, she got the call from small-town Denison, Texas where she accepted a job as an on-air meteorologist at KTEN-TV, right in tornado alley, covering severe weather from Sherman/Denison (North Texas) to Ada (Southern Oklahoma). After the most active tornado season Oklahoma had seen in May 2019 (105 tornadoes!) Alana is excited to join WeatherNation to cover weather all across the nation. If you're interested in following her on social media she can be found @alanacameronwx!