Updated Saturday 5:50 p.m.
Another December weekend, and another round of warm, wet and windy weather is pushing through Puget Sound. A soggy subtropically-rooted atmospheric river is once again taking aim at the Pacific Northwest, making for drenched pavement along I-5 from Canada to California. Rain has been heaviest over the Cascades, Olympics and Southwest Interior, and the Skokomish is once again under a flood warning in Mason County near Potlatch. Most other counties in Western Washington are under an overall flood watch as rivers and waterways continue to rise; those rivers most prone to flooding at this point will be the Snoqualmie and Nisqually.
While the passes and ski resorts picked up quite a lot of wet snow today, a rising snow level tonight will bring rain rather than snow to the lower passes. Overnight lows will barely drop into the upper 40s around the Sound tonight...warmer than our usual daytime HIGH temperatures for this time of year (average afternoon temps are in the mid-40s in late December). The rain will continue at a steady, moderate pace for most communities overnight.
By Sunday, while the rain continues to fall over the mountains, the persistent precipitation should give way to more widely scattered showers in the lowlands. Highs will still max out well into the 50s, which is about 10 degrees above average for this time of year.
Cooler air moves in on Monday, bringing down the snow levels (and hopefully the rivers) once again. Lingering rain will fall in the valleys, while the passes will be prone to more snow. Afternoon highs in Seattle and Tacoma will hover closer to 50.
Colder, relatively drier weather takes over as we approach Christmas Eve. Each day will feature a few showers, but we'll enjoy some nice sunny breaks, too. Highs will settle back into the middle 40s, with overnight lows in the 30s. Christmas Day still looks mainly dry and cool--a lot more like winter is supposed to!
Have a great night,
Meteorologist Shannon O'Donnell
The KOMO4 Forecast Team