360 Model Turn-around

 A few days ago, models were showing multiple strong ridges situating themselves over the Northwest. They hinted at above normal temperatures and almost a week without rain. But model trends drastically changed, almost overnight. And it looks like we are in for the most active weather week of the fall. Featuring chances of windstorms, flooding rain, lightning, mountain snow and maybe even some lowland snow for lucky (or unlucky) areas!

    This is going to be a very complex week for forecasting as models are extremely uncertain and continue to flip-flop. I will do my best to break it down. 


Act 1 (The entrance) -

On Saturday, a frontal system will cross the area. Temperatures are fairly chilly tonight, in the 30s in most places so I wouldn't be surprised if there were a couple of flakes mixed in areas above 500 ft. Temps will warm through the day with highs in the upper 40's. Not a lot else with this system, more or less an average November front with lowland rain and mountain snow. But, things get more interesting on Sunday.

Act 2 (The cooldown) - 

A strong cold front crosses the area on Sunday, ushering in much colder air behind it. Significant snowfall will occur in the Cascades. More than a foot of snow will fall in Snoqualmie and Stevens passes by the end of the weekend with more to come. Precipitation amounts will range from 0.5 to an inch. More on the coast. But the biggest talking point with this system will be what comes behind it. 


Colder air from the north seeps its way down south by Monday evening. Westerly flow behind the front will lead to the formation of a strong Puget Sound convergence zone. 

The Puget sound convergence zone occurs when westerly flow splits over the Olympics then collides over the Puget Sound leading to a intense band of precipitation. 



Act 3 (The PSCZ) -

The PSCZ is probably my favorite feature of our climate here. It is often the saviour of school kids, and brings unexpected surprises in the winter. After the front passes on Sunday, a PSCZ will likely form. It's too early to say where exactly, but I would say somewhere in Snohomish county. The intense precipitation would help bring snow levels down, so some of the higher hills around the Puget sound could see the first flakes of the season. Additional rainfall will occur for areas in the PSCZ. All of this could be accompanied by a lightning strike or two! Certainly looks to be an active start to the workweek!

 Act 4 ( Bombcyclone) - 

On Tuesday, an area of low pressure with its origins in the Pacific begins to rapidly deepen just off our coast.


It deepens to an extraordinary (I can't believe I'm saying this) 946 MB!!!! I don't even know how to put this is in perspective. If this were in the Atlantic, it would be the equivalent of cat-3 or cat-4 hurricane! Thankfully this looks to stay off the coast but it will bring a series of strong storms along with it.

Significant uncertainty remains so expect more updates to come.

Have a great day!!


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