Increasing Potential For Lowland Snow

The models are beginning to compromise with each other and a clearer picture is emerging. It is becoming increasingly likely that many lowland locations will see snow this weekend into next week. Significant uncertainty remains as to who sees snow, when, and how much of it. The overall forecast is going to be challenging and a lot of the details will likely not be ironed until the event is actually underway but I will do my best to provide the most likely scenarios. 


It all starts tonight, when a system moves through the area. This will bring the first real rainfall to the area in a while. At this point, the real cold, Arctic air is still hung up in Canada. On Friday evening, this cold air begins to move into Western Washington. Temperatures will drop significantly in a matter of hours. And as the winds from the north begin to collide with the southwesterly winds, a convergence zone will form. 

On Saturday morning, most of Western Washington will be close to the freezing mark and convergence zone will be raging. Under the zone, snow down to sea level is almost a guarantee. Where this convergence zone sets up is the real question. Most models seem to set it up in Snohomish county, although there would certainly be periods of time where this shifts south and north. It is always difficult to nail this feature down so it may just come down to a NOWcasting situation. The convergence zone will likely drop an inch or two of snow in parts of Snohomish county by Saturday night.

Then comes the potential for some more widespread lowland snow on Sunday. 

Sunday/Monday Snow

On Sunday, much of the cold air has made it's way into Western Washinton, scattered snow showers will continue across most of the area, with the possibility for some enhanced snow totals in areas of banding. As cold air spills off the BC coast and out over the Pacific. A system quickly spins up and rotates moisture back into Western Washington.




There is SIGNIFICANT uncertainty with this system. The exact position of the low will determine how much moisture will be available. At this point it is almost impossible for me to forecast snow totals so I will provide a lower end solution, a most likely one and a higher end one. 

Lower End - Low stays too far east and the cold air isn't really able to dig south. Most of the lowlands end up with some sloppy snow and nothing too impactful. I would give this scenario a 20 % chance of occuring, none of the models really have it that far east.

Most Likely - At this point, I think the Euro solution is the most likely, the low not too far east, and cold air is able to dig south. But moisture is lacking. Most lowlands would end up with 1-3 inches with higher amounts in banding. I am giving this scenario a 50 % chance of happening. 

Higher End - The GFS portrays the best higher end scenario for the Sunday/Monday event. Low is much closer to the coast and is moving very slowly. Cold air is definitely present and the low rotates moisture into Western Washington. This would be a pretty significant snowstorm for Western Washington with a widespread 3-8 inches of snow through Sunday and Monday. I am giving this one a 30 % chance of occurring.


I think that pretty much covers the uncertainty we have going into this event. 

I don't think that there is enough certainty in a major snow for widespread panic and stocking up, but would definitely encourage people to finish grocery shopping by Saturday. Wouldn't hurt to get enough food and milk for the week as it is always better to be prepared. It doesn't take a lot of snow to make driving very difficult in Western Washington. 

As always, will continue updating as we get closer. 


Have a good day!!
 




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