Mountain Weather Forecast

Weather Synopsis

The persistent ridge of high pressure remains centered over the region and continues to drift eastward. It won't let more than thin high clouds into the region through Wednesday night, but the pattern begins to break down on Thursday as weather starts to move into the region.

With dry conditions across the region, the main story remains the distribution of temperatures. Cold air is holding firm below around 5000 ft east of the Cascade Crest: Teens and 20's overnight, rising into the mid to upper 20s during the daytime. With light SW breezes continuing to bring warmer air and higher freezing levels into the region, the biggest question is how long that cold air can hold on. The cold pool may thin slightly on Tuesday night, but it begins to break down more in earnest on Wednesday, enabling milder air to move into the east slopes of the Cascades south of Lake Chelan as the day progresses. Pockets of cold air will remain in deep valleys.

The other story playing out results from the battleground between the air masses that occurs near the Cascade Crest and the mountain gaps in horizontal space, but also in the vertical dimension. Temperatures may rise sharply above around 5000 ft, given that the top of the tongue of warm air has a freezing level, which will remain in the 10,000-12,500 ft range.

Although high clouds will be more widespread and thicker over the Olympics and northern Cascades through Wednesday morning, expect increasing high clouds across the region by the afternoon. 

A trough digging southward offshore Wednesday night will lift a disturbance northward toward our region. Models differ regarding how far north the moisture will reach during the day on Thursday. At this time, it looks like it will reach Mt Hood late in the day, with some light flurry activity driven by upslope E flow in the East South Cascades.