Wet and Warm Thanksgiving Weekend After Large Amounts of High-Elevation Snow

The Thanksgiving has been generally wet and warm, but with large amounts of snow at higher elevations.  The temperatures at Seattle-Tacoma Airport and Stampede Pass (4000 ft) in the Cascades, tells the story (red and blue lines are average highs and lows this time of the year).   Minimum temperatures have been way above normal at both locations.  As I have noted in several blogs, this warmth is due to a persistent area of low pressure off our coast, which has brought in warmth and moisture.

The precipitation over the past day (24h ending 11 AM Saturday) has been impressive over the southern Olympics,  and north Cascades (2-3 inches in places).  You will note a profound rain shadow NE of the Olympics with only .07 inches over northern Whidbey Island (Ebey's Landing is one of my favorite winter walks).

The past seven days has been VERY wet along the coast, with some locations along the slopes of the Olympics and coast coastal mountains getting 10-20 inches)---see left panel below.  The right panel shows the difference from normal for the same period--unusually wet coast.  Some of the coastal river have hit or approached flood stage.

On Thursday and Friday, it was cool enough (and certainly wet enough) that the higher Cascades (above roughly 4000-4500 ft) got hit with several feet of snow (like three feet at Mount Baker ski area).  But it was too warm for the lower ski areas (and particularly Snoqualmie) to get anything on their lower slopes.

And it was made worse last night, when a warm front came through, pushing the snow level up to around 5000 ft.  The time-height cross section above Seattle shows this clearly (red is temperature in C, blue wind barbs, ordinate is pressure (850 is about 5000 ft), and time increases to the left (in UTC)

A weak frontal zone is now draped over the Northwest coast with light to moderate precipitation  (see radar below)

As the day goes on the front will slip eastward with precipitation stopping and the air cooling aloft.

Sunday morning will be a good time for outdoor activities (or to take part in the Seattle marathon) or to get across the passes.   Later Sunday, a strong (but cooler) frontal system will move in and will it should be raining over the lowland by dinner time.