No FastCast today…find current forecasts at weather.gov.
In the past 24-36 hours, a major snow and rain storm has impacted the Pacific Northwest. Incredible amounts of snow have fallen in the mountains and high rainfall totals have been recorded in the lowlands.
The photo below from a friend near Leavenworth shows just how much snow has fallen.
This photo was actually taken Thursday morning, and the property owner estimates that snow totals have reached 36-48 inches (3-4 feet) by Thursday evening…enough to almost bury this car.
As you would expect, the mountain passes have been hit quite hard by this storm. As of 7:45 PM Thursday, Snoqualmie, Stevens, White, and Blewett Passes are closed and will remain closed until Sunday. (More information here: WSDOT Twitter)
This major closure is due to very heavy snow and extremely dangerous avalanche conditions. When heavy, wet snow falls on top of dry snow, the chance of massive (and deadly) slab avalanches dramatically increases. WSDOT has stated that it is simply too dangerous for crews to work in avalanche zones, and it is the best option to keep the passes closed through Sunday. Some traffic camera images from the closed passes are below.
So what is ahead?
Mountain snow will continue through Friday, becoming confined to localized Convergence Zone bands, which can bring particularly high totals to Snoqualmie and Stevens Passes. The HRRR forecast for snow through Saturday is below.
Expect additional totals of 1-2 feet at the Passes (locally higher totals possible), with even higher amounts above 5,000 feet. Locally windy conditions are possible as well, with blowing and drifting snow possible. Avalanche danger will remain very high. Find avalanche conditions here: Northwest Avalanche Center (NWAC)
In the Lowlands, the main story will be rain, wind, and flooding. The ongoing atmospheric river has produced heavy rain totals of 1-4 inches in the Lowlands from Wednesday night to Thursday evening, and more rain is expected through Friday morning.
Below is the HRRR forecast for rain from 4 PM Thursday to Saturday afternoon.
This additional rain will bring storm totals to 2-5 inches in the Lowlands, 3-7 inches in the SW Interior (Thurston, Mason, and Lewis Counties), and 5-10 inches on the coast by late Friday.
As expected, urban, small stream, and river flooding is occurring and in the forecast. Urban Flood Advisories and Warnings are in effect through Friday, and river flooding is expected.
The Advanced Hydrologic Prediction Service forecast below shows expected flood stages on area rivers. (How to read: Major, Moderate, Minor, Bankfull)
Major, near record flooding is expected on the Neuwakum, Skookumchuck, and Chehalis Rivers near Centralia/Chehalis, Grand Mound, and Bucoda. Additionally, the Willapa, Grays, and Naselle Rivers in SW WA are expected to reach major flood stage. Highways impacted by this flooding include: US-12, US-101, SR-6, SR-4, and potentially on-ramps/off-ramps from I-5 in Centralia/Chehalis.
In the Lowlands, moderate flooding is expected on South Prarie and Issaquah Creeks, and minor flooding on the White, Snoqualmie, Tolt, Puyallup, Stillaguamish, and Snohomish Rivers.
One final hazard is wind overnight Thursday into Friday. With the recent rain and snowmelt, soils are incredibly saturated. This increases the chance of downed trees and power outages. The NAM forecast for gusts at 11 PM Thursday is below.
Expect gusts of 35-45 mph in the Lowlands, 40-50 mph in the North Sound and the North/Central Coast. Damaging 55-70 mph gusts will occur on the South WA coast and the Oregon Coast, and 40-50 mph gusts are forecast for the Willamette Valley.
With the very saturated soil, downed trees and power outages are expected, but will vary locally.
There’s a lot of weather going on right now…remember to listen to authorities and take precautions to protect yourself! Stay safe!
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