weatherblog

Expect lowland snow in areas Tuesday

This is a very tricky forecast indeed and while it is not optimal for a heavy snowfall event everywhere in the Western Washington lowlands, there will be some favored areas for significant impact, including from about Seattle north. The prime time for snowfall will be Tuesday afternoon into Tuesday evening.

This morning we have temps in the 20s and 30s with mainly calm wind and just a few flurries or very light snow showers to the south.

By late morning, expect some snow flurries to begin flying around the Puget Sound region. Initially, the lower atmosphere will be pretty dry so that will “eat up” a lot of the snowfall from late morning through early afternoon. But eventually the atmosphere will moisten and snow will reach the surface from about the Seattle and Tacoma areas north.

Later in the afternoon, warmer air surging in on a south wind will likely change the precipitation type to rain across the south Sound. Eventually that rain-snow line will get to Seattle but will it be before sunset or later on Tuesday evening or Tuesday night? That is a real dilemma in the forecast for the King County area below about 500 feet elevation. There will likely be a sharp gradient from about the Seattle area north into Snohomish County with wide range of snowfall amounts -- from Tr-3″ around Seattle to around 3-8″ north into Snohomish County and west into Kitsap County. This threat for heavier snow will also extend north into Skagit County and toward the Canadian border.

Farther south, the earlier onset of cold rain should keep the risk of impactful snow accumulation low. It will be windy area wide later today with gusts around 40-45 mph, but it will especially windy over the North Interior with gusts around 50 mph or higher.

Stay with us through the day as this is a very difficult forecast, with the forecast potentially changing quickly through the day into Tuesday night, as we discover how far north the warmer air will get. We have a number of Warnings to Advisories including Wind and Snow. I’ll be here all morning looking at possible totals and watching the precipitation starting later this morning and afternoon.

In the mountains, expect more than foot of snow Tuesday afternoon through Tuesday night.

Precipitation will be tapering by Wednesday morning and be mainly cold rain from about Everett south, but we’re likely to continue to have travel impacts, especially up north.

The forecast for beyond Wednesday is not very clear but it will be cold enough for lowland snow at times, all the way into the weekend. The timing of available moisture is unclear.