SEATTLE - Let's start with the potential for lowland snow Monday. The passage of a cold front will drop snow levels and temps, and heavy precipitation associated with the front may change over to wet snow. The most likely areas will be in the northern Olympic Peninsula, Cascade Foothills, and the convergence zone. If this verifies, travel impacts look to be minimal because the surface is so warm.
While models are in agreement with this brief wintry weather, there are a lot of factors that could bust this forecast and we may just see rain. Lowland snow is really difficult to forecast here! First of all, temps have been so mild, it hasn't been freezing cold. Plus, this system is coming from the Pacific and the ocean air is relatively mild so temps might not get cold enough. But if we learned anything from the year 2020, anything is possible. So stay tuned!
Otherwise, heavy rain will arrive late Sunday through Monday morning as a warm front lifts from south to north. A cold front will then move west to east through Monday bringing heavy downpours in the Sound by the afternoon and that potential for lowland snow. The mountain passes will certainly get snow as snow levels drop to 1500ft with the cold front Monday night.
A Flood Warning is in effect for the Skokomish River until further notice - moderate flooding is expected Monday. Rising rivers and elevated landslide risk will be the main threats over the next 3 days. Never drive through a flooded road.
We'll dry out by Tuesday with some sunshine through Thursday. Overnight lows will be very chilly, near if not freezing midweek. Another system will arrive by Christmas bringing a chance for rain through the first half of the weekend.
Have a great day!
-Q13 Meteorologist Grace Lim