Strong Winds, Heavy Rain, and More Flooding Expected on Monday

I will have a recap of the recent windstorm and flooding by 9 PM Tuesday. Stay tuned!

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FastCast—Sunday, Nov. 14 to Monday, Nov. 15:

After a warm, windy, and rainy Sunday, the active weather continues into Monday. The biggest threat will be winds, due to a low pressure center that will strengthen and move into British Columbia, bringing a large rise in pressure on Monday. Winds will increase through Sunday night, peaking from Monday morning to the afternoon. Expect strong gusts of 45-50 mph over the lowlands, potentially higher. Gusts of 55-65 mph are possible around Admiralty Inlet and on the coast. Tree damage and power outages are expected, especially due to very saturated soils. Expect rain totals of 0.3-0.75" of rain in the lowlands (potentially higher), and 0.5-2" in the Northwest Interior. As rain tapers Monday afternoon, the main issue will be river flooding. Record levels are expected on parts of rivers draining from the North Cascades and North Olympics. Flooding will last through Tuesday. Temperatures will remain in the upper 50s to low 60s through midday Monday, before dropping to the 40s by Monday evening. By Monday evening, snow levels will plummet to 1,500-2,000 feet, and Convergence Zone bands will bring 4-8" to the passes. Drier weather is in store for Tuesday!

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Continue reading the full blog below!

Due to a passing warm front, Sunday was a very warm day...by November standards! Highs around the area reached the low-mid 60s, and winds gusted 35-45 mph (locally stronger). Heavy rain fell north of Skagit County, with 1.5-3" in Whatcom & Skagit Counties on Sunday. Rivers began to rise again, with some (mainly north of I-90) returning to flood stage.

Another active day is on tap for Monday, featuring gusty winds, more rain, and major cooling (and rapidly dropping snow levels). 

Let's start with the wind. A low pressure system will quickly develop and move into British Columbia on Monday, and the associated sharp rise in air pressure will strengthen winds around the region. Below is the peak gust forecast from the HRRR Model on the VentuSky app.

Expect gusts of 45-50 mph around the lowlands. Isolated higher gusts (50-55 mph) are possible, especially near Puget Sound. Gusts of 55-65 mph are possible along the Strait of Juan de Fuca and on the coast. 

Winds will increase overnight, with the peak winds from Monday morning to early afternoon.

Due to this forecast, NWS Seattle has issued a Wind Advisory for the Interior Lowlands that is in effect until 4 PM Monday. The alert is below.

It is safe to expect gusts of at least 40-45 mph, with gusts in the 50 mph range very possible. Due to the fact that we have received huge amounts of rain in the past few weeks, soils are very saturated. This means that the threat of tree damage and power outages is highest with this storm than others this fall. Below is a graphic from AccuWeather illustrating saturated soil’s impact on trees.

Be prepared for strong winds, tree damage, and power outages on Monday. Winds will diminish somewhat by Monday evening, calming fully by Tuesday morning.

Now for the rain...a cold front will slowly move south through the area on Monday. Below is the UW forecast through 4 PM Monday.

Expect 0.5-0.75” in the lowlands, with less from approximately Tacoma southward. 0.75-3” is possible on the coast, with even more in the mountains. 1-3 inches are possible from Skagit County northward as the atmospheric river remains aimed at Northwest Washington and southern British Columbia.

All this rain will bring rises on area rivers yet again, especially for rivers north of I-90. Below is the flooding forecast from the Advanced Hydrologic Prediction Service.

Impactful flooding is expected. Red and purple dots mean moderate or major flooding. All time record high crests are possible on the Skagit, Nooksack, Elwha, and Dungeness Rivers on Monday and Tuesday. Damage is expected along these rivers. There will also be another round of flooding on the Snoqualmie, Skykomish, and Snohomish River system, peaking with major flooding near Monroe.

To top it all off, major cooling is expected on Monday as well. As the cold front moves through, temperatures will drop from the upper 50s to the low-mid 40s. By Tuesday morning, we’ll be in the upper 30s to low 40s! Snow levels will sharply decrease to 1,500-2,000 feet by Monday evening. In the wake of the cold front, Convergence Zone bands will bring snow to the passes. The UW snow forecast through 7 AM Tuesday is below.

Expect 4-8 inches of snow in these Convergence Zone bands. These are highly localized, so where they set up will determine which passes get the most snow (likely Stevens Pass).

Wow! That’s a lot of weather! A crazy Monday will end the recent rainy pattern (for the time being) with a bang! Expect dry days on Tuesday and Wednesday, before the next system arrives on Thursday, with more rain. The good news…no atmospheric rivers are in the forecast! 

Stay safe & stay tuned (on Twitter, follow our local weather experts)!