Tuesday Update

Folks...this is serious. So serious that Ivar's is canceling my presentation tomorrow night at their Mukilteo Landing Restaurant....looks like we will try March 9th.

There has been plenty of snow already in the convergence zone.....here is a recent radar image, See the band with green in the middle...that is the convergence zone.



Some locations have gotten 1-2 inches already. Take a look at recent cam in Everett:
Getting pretty white!

And here is a snow video taken in Lake Stevens this morning:




I have taken a look at the latest model runs this morning and they are amazingly consistent both in time and among the models. Although this give me confidence in their forecast, there is still uncertainty in exact positions of features and snow accumulations.

Here is the 24-h snowfall ending 4 AM on Thursday:There are a lot of subtlies in play here. First, the snow will be very banded, which means there will be a lot of horizontal structure (spatial variations in snowfall between neighboring locations). Second, for the early part of the period there will be significant rainshadowing (snow shadowing) off the Olympics under northwesterly flow...which means Kitsap and south Sound will have snow reduced. Third, a LOT of the action will be at the boundary between NE flow moving out of the Fraser and vicinity and southerly flow moving up the Sound. The southerly flow will be forced to rise by the cold, dense northerlies--producing enhanced precipitation (snow). That is why you see the heavy band between Seattle and Bellingham. No guarantees EXACTLY where that interface will lie. Upslope flow on the Olympics should produce heavy snow on the northern Olympic slopes.

And on Thursday, eastern Washington will get crushed by very strong northerly winds and extraordinarily cold temperatures (single digits and below zero).

So bottom line for snow. My prediction: South Seatttle--1-3 inches, North Seattle--2-5 inches, northern Snohomish (3-8 inches).

Good news for commuters and SDOT tomorrow: temperatures will remain above freezing, SO NO SOLID ICE LAYER like Nov 22, 2010.

I am planning to try another NOWCASTING experiment tomorrow (Wednesday). Frequent updates throughout the day on what is happening and will happen during the next few hours.

Finally, I would like to thank those that have contributed to the development of our local forecasting capability (upper right of this blog for more info)... I have already used some of the funds to replace some aging hardware.

PS: I am looking for video of Jim Forman if anyone has it or recording him tonight!