A cold front moves into Western Oregon and Washington tomorrow morning. At the same time we have a cool airmass overhead, along with colder and dry air pouring out of the Columbia River Gorge. The combination of these means we have a marginally good potential for snow to the lowest elevations again. ANYONE IN THE LOWEST ELEVATIONS MAY SEE SNOW FALLING, BUT ONLY SOME AREAS WILL GET SNOW STICKING ON THE GROUND.
Similar to Christmas Eve morning, pinpointing the locations where we see snow to the valley floor is tough. Unlike Christmas Eve, everyone will get steady precipitation west of the Cascades by 10am. So instead it’s all about temperatures then for your Sunday morning snow/rain forecast. Here’s the forecast graphic I used at 10pm:
I say west metro for the lowest sticking snow because there are strong hints based on the easterly flow and models that cold air will be deepest as it banks up right along the east side of the Coast Range and Tualatin Mtns. This is similar to the “Forest Grove Effect”, but kind of a weak version of what we’ve seen in the past. The 00z WRF-GFS and our RPM have a similar look. Tomorrow morning would be a good time to be in Vernonia, Buxton, Banks, or Forest Grove. Possibly St. Helens & Scappoose too. Also I think a dusting to 1″ is possible anywhere higher up in the West Hills.
Your next question is…”what if I live at 600′“? Then you’ll likely see conditions between those two text panels. No matter what someone tells you, we can’t forecast snow level with that much detail. I’ve seen snow level forecasts for 250′, 750′ etc… in the past. That drives me nuts. Precipitation intensity and location will affect snow level far more than elevation in most cases. For example at 1,000′ I had no snow Christmas Eve morning, yet people near sea level around Woodland/La Center had snow because heavier showers were falling in those locations.
For those of you travelling through the Coast Range tomorrow, I’d delay until the afternoon hours when the snow backs off. Roads should be better at that time.
For the Cascades and Gorge, the issue is that a lot of the moisture won’t even make it that far. As a result I said just 1-2” in the Gorge and it’ll probably be mainly wet on I-84 through the entire day. A few more inches in the Cascades won’t make any different on the snow-packed roads either.
Chief Meteorologist Mark Nelsen