PORTLAND, Ore. (KOIN) — Showers continue today with the best chance for dry breaks early this morning and again later tonight. We’re still in a light switch scenario for wet weather thanks to an upper level trough drawing in cooler than normal air. This feature moves out late tonight allowing for dry weather, but only briefly. And when we do dry out for a few hours temperatures will likely drop to near freezing around the valley by Friday morning.
A disturbance slides in from the north Friday – but what time does it arrive? If arrival is by morning then we could be talking about snow mixing in with rain at about 500 ft elevation. If it arrives later in the day, then temperatures will not support low elevation snow. I’ll risk being too general and say that we look at many factors for snow possibilities, one of which includes temperatures at 850 mb or approx. 5,000 feet. If temperatures are forecast to be near -8 degrees celsius there’s a decent chance snow may follow given all other elements support it.
This is the GFS snow total forecast 
This is the NAM snow total forecast
In the meantime, freezing and subfreezing temperatures are gripping the southern half of Oregon this morning with freeze warnings and frost advisories in effect.
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