Looming storms threaten rising rivers, tidal flooding in Whatcom County
A series of warm, wet storm systems heading toward Western Washington will increase the threat of landslides and river flooding, along with strong winds and waves that could inundate coastal areas of over the next several days.
Rain returns Friday, pausing Saturday before more storms sweep through the area from Sunday through Tuesday with moderate to heavy rain as part of an atmospheric river, the National Weather Service said in an online briefing.
A series of storms from Sunday through Wednesday has the potential to drop a foot of rain on top of snow in the mountains and 4 to 5 inches of rain in the lowlands.
Several scenarios are developing through early next week, and forecast models are diverging slightly about where the heaviest wind and rain will strike, Seattle meteorologists said.
“It is still within the realm of possibility that we could have a widespread river flooding event on our hands beginning next Tuesday,” meteorologist Dana Felton said Wednesday. “The landslide threat is minimal the next few days. The series of systems will eventually take its toll, with the landslide threat increasing slightly this weekend and rapidly early next week.”
Friday through Tuesday are the areas of greatest concern because the storms headed this way are subtropical, meaning that rain will fall in the North Cascades below about 6,000 feet, and melting snow causes rapid rises on the Nooksack and Skagit rivers.
Similar weather patterns were blamed for widespread flooding in 2020 and 2021, causing more than $150 million in damage in Whatcom County.
“Beginning Friday, the door will open to periods of moderate to heavy precipitation associated with moisture plumes originating from the subtropics. The successive nature could result in an increased risk of flooding as early as this weekend, but perhaps more likely by early next week,”: the weather service said online. “In addition, rainfall-driven landslide indices are also approaching seasonal thresholds and by early next week the landslide risk could become the highest yet seen this season.”
In addition, minor flooding appears likely along the Whatcom County coast over the Friday-Tuesday period as seasonal high tides coincide with strong winds.
“(Atmospheric) pressure, winds and waves will need to be monitored closely during this period to determine the potential for moderate or higher flooding,” the weather service said. “Current models indicate multiple days of water levels well above minor flood stage, and a few locations (particularly Cherry Point and Friday Harbor) flirting with moderate or higher flood levels. The actual level of impact will strongly depend on the overlap of low pressure and elevated winds, which are a challenge to nail down at this lead time.”
Seasonal high tides, often called “king tides,” arrive in December when the moon is at perigee – its closest point to the Earth.
High tides at Birch Bay will be above 10 feet Thursday through Wednesday, according to Tidetime.org.
Such high tides have caused damage to coastal Birch Bay Drive and homes and business near the village waterfront in the past.