A cool trough of low pressure moving into Washington from the north is expected to bring chilly and unsettled weather to the region this weekend. In fact, the word snow will have to re-enter the dialogue, since a few areas have already seen light accumulations, while others are poised to soon receive this season’s first dose of the white stuff.
Saturday looks to begin with cool but dry weather, as western rain chances increase during the day. Precipitation should spread eastward overnight, and is likely to persist into Sunday. The main question is going to be one of precipitation type, with cooler air to the north and greater precipitation totals in the south. While many southern areas east of the Cascades are anticipated to only see rain or a mix with non-accumulating snow, some lowland central/northern areas, especially near the Cascades, could observe measurable snowfall. Far northern sections are forecast to receive less precipitation with this system. Thus, there may still be a zone where there is sufficient overlap of cool temperatures and appreciable moisture for measurable snow to accumulate. For western Washington, southern rain is likely, but for isolated, favored areas such as in the lee of the Olympics, accumulating snow is possible.
For early next week, drier yet continued cool conditions can be expected. Another wet yet warmer system is possible for later next week, but the details remain unclear. In any case, milder temperatures are likely later in the period. Therefore, the general progression of this outlook interval will be from cool, unsettled and even snowy to cool and dry, and eventually to milder and variably unsettled. Regardless of whether your city experiences their first snowfall of the season during this ongoing winter preview, the next several days should still serve as a reminder that the real thing may not be too far away.
Preliminary Estimate of Key Boundaries for the Weekend Snow Event:
• For central/eastern Washington: Light snow accumulations possible north of a Yakima to Moses Lake to Pullman line, and drier in the far north
• Non-accumulating snow or a mix near and just south of that line, with rain in the Lower Columbia Basin around the Tri-Cities and Walla Walla
• Given that the maximum lowland precipitation (for central/eastern Washington) may occur near the east slopes of the Cascades, the region of highest lowland snow totals may occur somewhere around the Waterville Plateau
• Rain or snow for western areas, with isolated spots of appreciable accumulation possible
Western Washington Weekend
• Rain or showers developing on Saturday, with rain or possibly snow on Saturday night. (The National Weather Service in Portland forecasts heavy rain Saturday night on the southwest coast.)
• Showers on Sunday.
• Highs in the 40s to around 50 on Saturday, and 40s to low 50s on Sunday.
• Lows in the mid 20s to 30s on Saturday morning, and 30s to mid 40s on Sunday morning.
• Mostly dry early. Rain likely later in the week.
• Highs in the mid 40s to low 50s on Monday, and warmer later in the week.
• Lows in the mid 20s to 30s on Monday morning, and warmer later in the week.