A little more than 48 hours before the season’s first snowflakes are set to fly, models are reaching more of a consensus on how this weekend’s wintry weather will play out.
While the devil truly is in the details–and the details will certainly fluctuate as we get closer to Sunday–this much is certain: a strong cold front will barrel through the area Saturday afternoon, enveloping the region in a chilly rain. Temperatures will start out in the low 40s, but will quickly plummet into the mid-30s by Saturday evening (oddly enough, it will likely be warmer Saturday night than it was last night, when SeaTac fell to the freezing mark before the nine o’clock hour).
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| High-resolution UW model showing 24-hour snow amounts through Sunday at 4 p.m. Note the trace to 1″ amounts around Seattle, and the higher amounts east and north of the city. |
By early Sunday morning, temperatures across the Sound will be hovering in the low 30s, with plenty of moisture around. Showers are almost certain to be in the form of snow, as the snow level falls to sea level. The catch, however, is that winds at the surface will be out of the west or northwest, meaning they’ll be moderated by the always-mild Pacific Ocean as they blow onshore. This could be enough to warm the lower levels of the air by one or two degrees, meaning that places around Seattle are likely to see non-sticking snow showers during the daytime hours, as the warmer winds from the Pacific hold temperatures juuuust above freezing.
Farther away from Seattle, where there is less of a marine influence, snow showers are more likely to stick. This includes the greater Eastside, where 1 to 2 inches of snow could accumulate by Sunday evening. Further north–especially from Mt. Vernon to Bellingham–up to 4 inches of snow accumulation is possible, as the air there is more likely to be chilled by winds coming out of Canada’s cold Fraser River Valley.
The other major caveat to Sunday’s weather is, of course, the Puget Sound Convergence Zone. A strong Zone is likely to set up shop somewhere early on Sunday–anywhere from North Seattle to Mount Vernon. Right now, the models are all over the map as to where exactly the Zone will form. Given past history, I would expect the Zone to form in the Stanwood vicinity (northern Snohomish County)–for some reason, it seems like snow-producing Convergence Zones always target that area in particular. Be on the lookout for heavy snow–up to 6 inches’ worth–if you’re going to be around there early Sunday morning!
As we get into Monday, the snow showers will abate, but the cold will remain. High temperatures on Monday will only top out in the mid-30s–possibly not even that high in areas where snow cover exists (this means you, Stanwood)! Come Tuesday, models offer a variety of different solutions, from a brief snow-to-rain event (the American model), to the snowstorm of the decade (the European model).
At this point, it’s impossible to tell which model will end up correct–the European generally outperforms the American in these situations, but this is Seattle, where major snowstorms are very hard to come by.
In any case, our lame winter is about to get a whole lot more exciting. Stay tuned, and enjoy the snow!
