Mountain Weather Forecast

Weather Synopsis

A tricky weather pattern will play out across the Pacific Northwest over the next 24-30 hours, bringing precipitation, gusty winds, and gradually cooling temperatures. Big questions like how much, how strong, and where are tough to answer. A cut-off low pressure located off the southern Oregon coast will slowly drift inland this evening, spinning waves of precipitation into the area from the S and SE. This setup flips the normal script, focusing the bulk of the precipitation not only on the southern portion of the region, but also along the east-side zones. Areas near Ahtanum Meadows, Bumping Lake, and the Wenatchee Mountains could see the highest precipitation totals. Colder air closer to the low pressure center will also help temperatures cool more significantly in the southern zones. Conversely, locations further north will remain mild, with temperatures in the low 40s. 

Rain and high elevation should increase through the evening hours as the Low starts to move inland. Heavy bands of precipitation could lead to wide discrepancies in rain/snow totals. If you happen to be under one of these intense showers, it could feel very stormy. Along with the heavier precipitation, expect ridgeline winds to increase significantly. Gusty conditions should form from Hwy 2 south, with the windiest conditions expected near Snoqualmie Pass, along the southern Cascade Crest, and at Mt Hood. 

Precipitation peaks right around sunrise. There's quite a bit of uncertainty about how far north the major bands of rain and snow reach. They could extend as far north as the Mountain Loop Hwy, or get hung up further south. By mid morning, the Low travels far enough inland that the upper level winds make a 180, and begin to blow form the NW. This should decrease precipitation along the east slopes of the Cascades and focus showers on the western and pass zones. With the shift in winds, there may also be some breaks in the clouds. The best chance of sunshine will come near and east of the crest in the afternoon. Closer to the core of the moisture, Mt Hood could see very stormy conditions all day long. 

By late afternoon to early evening, upper air winds shift more northerly, ushering in drier and cooler air into the region. Showers should slowly taper Wednesday night, with only a few sprinkles left by Thursday morning. Low level moisture could get trapped in the Puget Sound, leading to low clouds banked up against the mountains, but overall the trend will be for drying and clearing as a high pressure ridge builds in the northern Pacific.