The National Weather Service has issued a Winter Storm Watch for the south Willamette Valley for Thursday, that includes Albany/Corvallis down to Eugene. In the valleys, a winter storm watch is issued when 4″ of snow is possible.
1. We have a greater than normal level of uncertainty with the forecast for the next 3 days. Models are in quite a bit of disagreement about how much snow falls where and when.
2. Whatever falls in the valley from Kelso to Portland to Eugene through Saturday should be frozen (snow or freezing rain).
3. You should be flexible with work and other plans Thursday, Friday and Saturday. And assume the forecast could change with just 24 hours notice.
4. A very good chance areas south of the Portland metro area get a decent snowstorm in the next 2 days.
I mentioned this in last night’s posting, but now it’s even worse. A wide variety of model solutions for the next 2-3 days. ALL models show some surface low pressure systems tracking along the arctic air boundary draped across the middle of Oregon. ALL bring moisture at least through southern Oregon. But SOME bring it much farther north, right into the Portland metro area and even Longview/Kelso.
Here is our RPM model forecast (it isn’t always right on!) for noon tomorrow. Light snow that starts in the southern valley slips north and starts showing up tomorrow afternoon in the metro area.
and then at 4pm tomorrow showing the heavier snow down the valley.
and the total snowfall forecast by Friday morning. The 2″ line cuts across the south side of the Portland metro area with 4-8″ south of Salem!
But look at the snow accumulation forecast from UW’s reliable WRF-GFS model:
much farther south! In this case there would be NO snow in the valley tomorrow, but a nice snowstorm at Roseburg. Now these are only two models, we have more, but I wanted to illustrate what a tough forecast it is for tomorrow. I should also point out both were “initialized” at the same time, early this morning. Just 1/2 hour ago another very trusty model came in, the ECMWF (the European model). It has decided to run the surface low pressure directly into the north valley instead, plunging the metro area and valley into a midday/afternoon snowstorm with gusty east wind and temps in the 20s! Here is the 4pm precipitation forecast (with surface pressure lines too):
This could produce 2-4″ in time for the afternoon commute…hmmm.
Luckily we have a few more models that come out this afternoon, then a whole bunch more this evening. Hopefully they will come into better agreement. We don’t need an “Atlanta-Style” commute Thursday afternoon.
The main message: There is a very good chance for at least some snow in the central/southern valley (and central coast) tomorrow, and it MAY spread farther north into the metro area, but we’re not sure yet.
Chief Meteorologist Mark Nelsen