Mountain Weather Forecast

Weather Synopsis

The Pacific NW has entered a week of more active weather. A weak low-pressure center tracking northward off the Oregon Coast on Thursday has ended an unseasonably strong ridge of high pressure. Light rain and higher elevation snow have spread into the southern and central Cascades west of the Crest, while snow or a wintry mix can be found near or east of the Crest. Snow levels are rising as this wave moves through, so the question becomes how long and how thick is the cold pool, and how quickly will increasing SW winds displace the cold air Thursday night into Friday. To put it mildly, this is a very tricky precipitation type forecast, and you should expect a lot of uncertainty if you're traveling near or east of the Cascade Crest.

The overall rain/snow line should rise to around 8000 ft at Mt Hood, 7000 ft for Mt Rainier, and 3500 ft near the Canadian Border. It will begin near the surface east of the Cascade Crest, with light precipitation expanding throughout the region during the evening hours. As the low tracks through Western Washington overnight, SW winds increase to moderate in the southern and central Cascades. These winds will scour out much of the cold air pool in the southern Washington Cascades by early evening, then Snoqualmie Pass by late evening, and Stevens Pass by Friday morning. Expect a 3-9-hour period of freezing rain potential and very hazardous driving conditions if enough low-level cold air lingers.

The moderate precipitation exits the region by 10 AM Friday, leaving light rain and snow, mainly over the central Cascades and the Mountain Loop, with snow levels in the 5000-6000 ft range.

A deeper closed low moves into the waters off the Oregon coast, maintaining some light precipitation, including an upslope component along the E slopes of the Cascades, Friday night. Another wave of precipitation moves over the region from SW to NE on Saturday with continued E flow.