Tuesday Snow Update

Quick forecast update. The storm tracked slightly further north than modeled, meaning that mild southerlies (and rain) extended to the King/Snohomish County line instead of staying south of Seattle. The Everett area saw 1-3 inches overnight, depending on elevation, and totals increased northward from there. Whatcom County got clobbered, with reports of over a foot near Birch Bay near the US/Canadian Border.

<blockquote class=”twitter-tweet”><p lang=”en” dir=”ltr”>Birch Bay via my FB page! Shared with permission. <a href=”https://twitter.com/hashtag/wawx?src=hash&amp;ref_src=twsrc%5Etfw”>#wawx</a> <a href=”https://twitter.com/NWSSeattle?ref_src=twsrc%5Etfw”>@NWSSeattle</a> <a href=”https://t.co/e2u12LtdsB”>pic.twitter.com/e2u12LtdsB</a></p>&mdash; Randy Small – Whatcom County Weather (@RandySmall) <a href=”https://twitter.com/RandySmall/status/1605219065949454336?ref_src=twsrc%5Etfw”>December 20, 2022</a></blockquote> <script async src=”https://platform.twitter.com/widgets.js” charset=”utf-8″></script>

However, Seattle is now FINALLY seeing accumulating snow as the storm’s cold front moves south and these mild southerlies transition to cold northerlies. Beginning around 8:30 am, rain switched to snow here in Magnuson Park, and we have close to an inch on the ground now. I expect the Seattle area could see a trace-3 inches before the snow tapers off in the afternoon, depending on elevation and location (further north/higher elevation= more snow). Less than initially expected, but not a complete bust either.

Current observations show the arctic front’s progression southward.

Here’s the culprit for the sudden changeover to snow across Seattle this morning. An arctic front came through Seattle around 8am, dropping temps from the upper 30/lower 40s to the lower 30s. Trace – 3″ possible in Seattle before snow tapers in late am/early pm #wawx #seattlesnow pic.twitter.com/F9aXeagnen

— Charlie Phillips (@WeatherPhillips) December 20, 2022

3-day trace at Station E9877 in North Seattle. Temps fell from 38 at 7:50 to 30 by 10:10. Wow! pic.twitter.com/wKDRTTXV8f

— Charlie Phillips (@WeatherPhillips) December 20, 2022

The front is also visible on radar… note the sharp, bright line extending from Aberdeen through Seattle.

Front is very visible on radar as well. Note the thin line of heavy precip extending from North Aberdeen through Seattle – this marks the exact position of the front and associated wind shift. #wawx #seattlesnow pic.twitter.com/zyDkzaEQ4V

— Charlie Phillips (@WeatherPhillips) December 20, 2022

With temps now below freezing and forecast to stay that way through at least Thursday night/Friday morning, any snow that has fallen will stick onto roads and create treacherous conditions for travel. Many schools have closed early for winter break, and if you need to do some last-minute Christmas shopping, please exercise extreme caution when traveling.

The main concern this week continues to be Thursday and potentially Friday due to frigid temperatures (highs in mid-20s for Seattle/Portland and single digits east of Cascades on Thursday), the potential for freezing rain, and extremely strong easterly winds in the Cascade foothills, Columbia River Gorge, and Portland metro area. I am particularly concerned about freezing rain and power outages for the Portland/Willamette Valley area in this setup… individuals should charge devices and power companies should prepare for widespread outages. More to come in future blogs.