Atmospheric river clips Oregon early in the week


PORTLAND, Ore. (KOIN) – It took six days into December to register our first measurable rainfall in Portland — and it won’t take very long this week to back that up with more measurable rain.

Monday is going to begin with patchy fog, with the heaviest of the fog south. It’s likely low clouds will stick around Portland and Vancouver in stratiform. Clouds will hang around for most the day Monday, but there may be some breaks in the afternoon.

The measurable rain will move in on Tuesday. Check out the day planner below to get a good idea of your day tomorrow. It’s possible we hit the lower 50s, but I think with the morning fog and clouds, we may be closer to average in the upper 40s. Not a huge difference.

The system that is out in the Gulf of Alaska is creating some energized swell. The wave forecast is painting some impressive wave height. That will impact the Oregon and Washington coast come Monday morning. It was already noticeable on Sunday; it will increase Monday.

There is a High Surf Advisory Monday morning to Tuesday morning for the communities up and down the Oregon coast in the graphic below. Please be weary of sneaker waves and just aggressive conditions out there.

With that, weather models start to show that rain getting closer by Monday night. The 4 p.m. forecast has the rain moving into the Olympic Peninsula and that will eventually sag south to Oregon.

The atmospheric river that will cast that moisture over areas of Portland by Tuesday. Focus on the cloud cover for Monday afternoon, where there looks to be a dry slot extending through areas of the Willamette Valley. I wouldn’t anticipate a lot of sunshine on Monday, but we do have an opportunity to see a peek here or there. Air stagnation may still be a problem for areas of the Columbia Basin, improving on Tuesday as this system moves in.

If you’re hoping for a little dry time this week, Monday and Wednesday are your days. Tuesday, Thursday and Saturday will bring in the heavier rain. This week will feel a lot different that our first week of December. We are likely to pick up over an inch of rain this week, which is exactly what we need. Tuesday will not be a high powered atmospheric river for Portland, but we may have some impressive totals in areas like Astoria and Long Beach, Washington.

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