TONIGHT: Cloudy with local light snow, especially along the Cascade foothills. Minor accumulations of up to an inch possible in those areas. Elsewhere, only trace amounts are likely, especially from Seattle southward. Lows in the upper 20's to low 30's. The precipitation could become mixed with or changing to light freezing drizzle or freezing rain, especially after midnight.
Puget Sound Forecast: Areas of freezing drizzle or light freezing rain will be possible (it's a slight chance) after midnight or in the early morning hours, changing to rain later in the morning or early afternoon with slow warming. Highs in the mid to upper 30's. Most, if not all areas, should have changed to rain (as a result of warming) by mid afternoon.
Coast Forecast: Mostly cloudy with mixed rain/snow/freezing drizzle changing to rain in the morning. Highs in the low to mid 40's.
Mountain Forecast: Snow at times; 2-6 inches possible. Pass highs in the mid to upper 20's, west winds to 10 mph.
Eastern Washington: Mostly cloudy; a chance of light snow especially near Spokane and Walla Walla. Highs in the 20's.
WEATHER OUTLOOK/LONG RANGE TREND:
The high pressure that had blocked the flow of moist air, instead directing very dry and very cold air from the north and northeast is weakening and receding to the south. That's now pushing moist air from over the Pacific into western Washington. Right now, that moist air is sliding over the cold air near the surface. That's why we're seeing areas of light snow develop. The flow of moist air is weak, and that's why I don't expect significant snow in most areas, with the exception of areas where that moist air will get a little added boost upward. That would include the area along or near the Cascade foothills...where there could be local accumulations of perhaps an inch. Most other areas, including Seattle and Tacoma, may see trace amounts or perhaps fractions of an inch...if any.
As the night wears on, the layer of cold air trapped near the surface will thin and the air aloft will continue to warm. That means rain falling into a layer of sub-freezing air-at least in places...which in turn means local freezing drizzle or freezing rain. We're not talking significant amounts...certainly nothing like January of 2012. But it only takes a very thin layer of ice to make driving, cycling or walking problematic! This will be most likely overnight or early Tuesday morning.
The layer of cold, sub-freezing air will continue to erode Tuesday...most areas should see precipitation change to rain and temperatures above freezing by late morning to early afternoon if not before. That warming will probably be delayed over western Whatcom and Skagit counties. Expect highs in the mid to upper 30's.
Rain showers will remain possible into Wednesday, with another/warmer system Thursday for a rainy/breezy day with highs in the mid 40's. Showers are likely to linger Friday, with increasing rain and wind Saturday...and decreasing showers Sunday. This pattern is likely to produce repeated snow in the mountains...promising better skiing this weekend!
Jeff Renner / KING 5 Chief Meteorologist