This story was originally published on MyNorthwest.com
The National Oceanic and Atmospheric Administration (NOAA) is sending its famous surveillance aircraft into a powerful storm system that threatens widespread flooding and damaging winds for Western Washington Monday through Wednesday.
The approaching atmospheric river barreling toward Western Washington is powerful enough to warrant a rare deployment: NOAA is sending its hurricane-hunting aircraft directly into the storm system Monday, a dramatic move that underscores the impact of the approaching weather event.
During hurricane season, the aircraft flies hurricanes over the East and Gulf Coasts to collect critical data. Now, during the off-season, the plane is heading to the Pacific Northwest.
A specialized reconnaissance aircraft will be crossing the Pacific Ocean off the coast of Washington throughout Monday, dropping instruments into the storm to collect real-time data that will help meteorologists refine their forecasts as the system makes landfall.
“Instead of just sitting around doing nothing during hurricane season, NOAA and the Air Force sometimes send hurricane hunters out here into our neck of the woods to fly into some of our strongest hurricanes,” meteorologist Scott Sistek, study author. Weather in the Emerald City blogexplained. “By sending a hurricane hunter into our storms, we can get a lot more verified data in real time that we can feed into our computer models.”
This enhanced data is becoming critical as forecasters track a storm system that could bring three to five inches of rain to the Seattle metro area and lead to severe flooding in several rivers by Tuesday and Wednesday.
Two waves of damaging winds struck on Monday.
Before the heaviest rain arrives, gusty winds will hit the region in two distinct bursts on Monday, creating hazardous conditions for the daytime commute.
The first wave is targeting areas from Seattle south through Everett, with winds picking up around midday and continuing into the early evening. Gusts of 40-45 mph are expected throughout the region, with isolated gusts reaching 50 mph.
“Usually when we have a hurricane, we talk mostly about the north, like the San Juan Islands, but this one is mostly about the south,” Sistek said, noting the unusual wind pattern.
Once the storm passes, a second gust of wind will follow, sending westerly winds into the Strait of Juan de Fuca. This post-frontal blast will impact Port Angeles, Sequim, Whidbey Island, and parts of western Snohomish and southwestern Skagit counties with sustained winds of 40-45 mph.
The double winds are occurring on soil saturated from recent rains, raising concerns about trees falling onto power lines and roads.
Major flooding expected on Western Washington rivers
The Snoqualmie River is among the most significant flood threats, with forecasts calling for severe flooding at both Carnation and Snoqualmie Falls by Tuesday. Residents in flood-prone areas of the Snoqualmie Valley should prepare for water to flood farm fields and cross roadways.
The Skagit River is hovering within a fraction of an inch of major flood stage, and the advancing flood will likely push it over the threshold. Other rivers at risk of serious flooding include the Skykomish River in Monroe and the Cowlitz River in southwest Washington.
“I don't think any river can slip past without some minor flooding or without reaching flood stage,” Sistek warned. “For other rivers, we're not talking about historic floods, we're talking about floods that you'll notice and need to be careful about.”
Flooding impacts are expected to peak on Tuesday and Wednesday as rainfall accumulates and rivers reach peaks.
Seattle will get a month's worth of rainfall in just a few days
The atmospheric river will drop three to five inches of rain in the Seattle area between Monday and Wednesday, roughly equivalent to the city's average rainfall for all of November or December compressed into just three to five days.
“This goes beyond just rain in Seattle,” Sistek said. “Usually a storm comes in and it can get up to a half-inch. Some of our stronger storms drop maybe an inch of rain a day. That's more rain than we're used to.”
The heaviest precipitation will be concentrated from Seattle south through Tacoma and the South Cascades to Portland. While Whatcom County and other far northern areas will see significant amounts of precipitation, extreme precipitation has shifted slightly southward compared to previous forecasts.
Storm downgraded to Category 4 but still dangerous
Forecasters have adjusted the atmospheric river's classification from a Category 5 to a Category 4 on a scale of five, although meteorologists warn it remains an exceptionally strong system.
“You're playing semantics here. 4 is still a very strong atmospheric river,” Sistek explained. “It’s just a criterion by which they get a 5; it dropped a little lower than that.”
Hurricane hunter data collected Monday could provide more precise measurements that could adjust the storm's rating or refine flood forecasts for specific river basins. The plane will drop instruments through the storm system, measuring conditions that satellites and scattered buoy reports can't capture in detail.
Urban flooding and landslides threaten even non-river areas
Seattle residents who don't live near rivers still face significant risk from prolonged and heavy rainfall.
Clogged storm drains can cause flooding in urban areas, and saturated hillsides and bluffs can collapse in landslides. Anyone living on or near slopes should closely monitor conditions and watch for signs of ground movement.
Road closures are likely in landslide-prone areas. One area where landslides frequently occur is along the West Valley Highway, an important alternative route for commuters experiencing lane closures on Highway 167 in the Sumner, Pacific and Auburn corridors.
What should you do now
Meteorologists and emergency officials are urging Western Washington residents to take the following steps:
Before the storm
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Clear leaves and debris from gutters, downspouts and storm drains.
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Secure outdoor furniture, trash cans and other items that could be blown away.
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Charge phones and electronic devices during a power outage
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Availability of flashlights, batteries and essentials.
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Know your flood risk and evacuation routes
During a storm
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Never drive through standing water on the roadway.
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Avoid unnecessary travel during peak wind and rain conditions Monday afternoon through Wednesday.
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Stay away from downed power lines
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Monitor river levels if you live in flooded areas.
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Watch for landslide warning signs near hillsides.
The widespread impacts mark this as a significant weather event for the region, lasting two to five years, not the most extreme on record, but well beyond typical December precipitation amounts.
As hurricane-hunting planes provide meteorologists with the most detailed look yet at the hurricane's inner workings, forecasters will continue to update forecasts through Monday, when the atmospheric river makes landfall and begins its wet and windy advance into the Pacific Northwest.
For the latest weather news and river forecasts, follow meteorologist Scott Sistek at EmeraldCityWeather.com.
Charlie Harger – host Seattle Morning News on radio “KIRO”. You can read more of his stories and comments. Here. Follow Charlie by X and write him an email Here.
