THURSDAY NIGHT (11/12): Rain is moving in and mountain snow will be falling starting in the next few hours in the Cascades. This sort of weather system – with a front that stalls overnight along the Cascades – usually produces large snowflakes or clumps of snow and high snowfall rates. Pass travel will become difficult to impossible not too long after nightfall, and continue to be very bad going through Friday morning. I expect a foot or more of snow by daylight Friday in the passes and more at the higher resorts and volcanoes. Snow level is above 2,000 feet.
In the lowlands, it’s getting breezy out there and wind gusts in the 25-30mph range will be common this evening up until around midnight around the Sound. Up north, winds have already been gusting to 45mph+ at Whidbey Island and areas mainly north/northwest of Everett are under a Wind Advisory into Friday morning for gusts in that 45mph+ range in more prone spots along the water.
It will also pour rain for most of us through tonight with 0.50-1.25″ of rain common, except in the central and north Sound (Bremerton, Everett, Seattle) where rain shadowing in the lee of the Olympic Mountains will keep rainfall totals lower. Still, urban flooding from clogged storm drains will become increasingly common this evening and overnight. This will also be a problem for the Friday morning commute, especially before dawn.
FRIDAY: The great news is the storm that was looking like it could take shape a few thousand miles out in the Pacific decided it didn’t want to become a compact and fierce storm, but instead just a lazy “open wave” as we call it. This wave, or trough of low pressure, will move across the area Friday bringing breezy weather with wind gusts in the 25-35mph range but nothing extreme. Snow will continue to fall in the mountains with another foot of snow on top of what falls tonight, with the exception of Snoqualmie Pass which might have a changeover to rain on Friday morning which will limit further snow amounts to the “less than a foot” range on Friday. Still pass travel trouble will be common.
In the lowlands, aside from the aforementioned breezes, it’ll be showery but not raining constantly. There is a slim chance of a thunderstorm Friday afternoon, particularly nearer the coast but we’ll be watching for any lightning strikes which could happen anywhere. They just won’t be that common.
At the Pacific beaches, there will be some beach erosion and waves in the 13-16 foot range but nothing extreme. There could also be some minor flooding with high tide on the west and south-facing locations of Puget Sound in the early-mid afternoon Friday (think 12-3pm) as tides will be abnormally high. This shouldn’t be a big deal and is common around King tide season. Some spots like Mukilteo and Edmonds could have some of the waterfront parking lots or trails swamped briefly.
Highs will be in the 40s to around 50 in the lowlands Friday.
SATURDAY: Showers and sunbreaks but not as windy. Some mountain snow will continue to fall but hopefully travel will be better through the passes.
SUNDAY: Breezy again early in the day with rain, turning to afternoon showers. More mountain snow.
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