Today, I was working outside after putting a turkey in the oven...it was TROPICAL outside, with humid air approaching 60F. Many local reporting stations exceeded 60F, with some in the Tri-cities hitting 70F. It was 73F in Honolulu at 3 PM.
The tropical air came in on Tuesday with an amazing warm front. Here is a trace of the wind speed, wind direction, temperature, and dew point temperature that day. Around 01Z (about 5 PM), the temperature increased about 8F in an hour, the winds shifted to the south, and wind speed increased rapidly. A magnificent warm front--a rarity here in the NW.
We can see exactly where the air over Seattle has been coming from using the NOAA Hysplit model. Here is a trajectory (the path of the air) ending over Seattle at 4 AM Thursday for a period of 96 hour. Started a bit northeast of Hawaii.
But everything will change radically on Friday. The Arctic is coming...to YOU.
Early Friday afternoon a strong cold front...in this case an ARCTIC FRONT...will be moving into western Washington. Here is the latest WRF model prediction valid at 8 AM Friday: big temperature drop behind it, although the coldest air (purple and brown) is still in British Columbia.
The front will move southward during the day and by Saturday at 4 AM, we will have modified Arctic air entering the region (see graphic).
And what about snow? Right now if looks like the temperatures will be too warm for snow in the lowlands of western Washington on Friday, but there will be plenty of precipitation in terms of rain.
Here is the 24h snowfall ending 4 PM Friday. Lots in the mountains but nothing near sea level.