We are headed out west for the forecast. British Columbia was on the receiving end of the “atmospheric river” this week. How does that translate a little further south, to Portland?

At 1104AM, PT, Portland was reporting a temperature of 48 degrees with overcast skies. There were lingering low clouds along the Cascades, but clearing at low levels with some insolation. The jet stream was visible on satellite, given some mid layered clouds over Oregon. An upper level trough is off kilter, directed east to west off shore from Oregon. As it comes to alignment with a more zonal flow pattern, cold air will move into western Oregon, and there are freeze warnings in parts of the region.
As the trough pivots on land, it is expected to excrete some of it’s moisture over the center of the state, which may include a bit of rain in Portland on Wednesday evening, though most of the activity will be further south, and further inland. Behind this boundary, moist onshore flow will continue from the Pacific, which will lead to a cloudy and fairly dreary Thursday morning, with some breaks in the afternoon.
Tomorrow – Mostly cloudy, with a chance of rain in the evening, High 57, Low 43
Thursday – Cloudy early, clearing late. High 59, Low 41

TWC: Tomorrow – Partly cloudy skies, High 58, Low 41
Thursday – Partly cloudy. High 60, Low 41

AW: Tomorrow – Times of clouds and sun High 58, Low 42
Thursday – Mostly cloudy High 59, Low 42

NWS: Tomorrow – Mostly cloudy, then gradually becoming sunny, High 57, Low 42
Thursday – Mostly sunny, High 57, Low 40

WB: Tomorrow – Mostly cloudy in the morning then mostly sunny with a slight chance of rain showers in the afternoon, High 54, Low 43
Thursday – Mostly sunny, High 55, Low 42

WN: Tomorrow – Partly cloudy with light rain showers, High 54, Low 43
Thursday – Partly cloudy, High 54, Low 42

CLI: Tomorrow – Light Rain showers, High 59, Low 43
Thursday – Partly cloudy, High 60, Low 43

Not everyone is on board with rain, which makes sense. I think the threat is low, but given the lead time is still over 24 hours, I’m not ready to pull it out of the forecast yet. You can certainly follow the course of the jet stream on the satellite imagery.