I think it’s very unlikely we see anything other than a spot or two of ice in a valley out near the Coast Range late tomorrow morning. The chance for a metro-wide glazing of ice? About 10%
Look at the high temps for today; warmest in 8 days here in Portland:
You can see where the mild east wind cut through the middle of the metro area (at least above the surface) and helped to clear the fog out. Anywhere north or south of us stayed near or below freezing.
This doesn’t affect tomorrow’s weather at all because now with the clear sky temps have dropped below freezing again; back to the usual freezing fog programming overnight and tomorrow morning.
I don’t have any new thoughts on tomorrow’s chance for freezing rain west of the Cascades, EXCEPT that this evening’s models are slightly slower with the rain tomorrow. That’s very good news if you don’t want ice on roads. Our RPM precip forecast at 11am shows the edge of rain just coming down off the Coast Range into the farthest western portions of the metro area:
and by 1pm it has spread to about Camas/Gresham.
The 00z WRF-GFS is even slower, holding off precip for most of us by 1pm. I’ve never seen freezing rain start DURING THE DAY (after 9am) unless the temperature is real cold…like 25 or so. Not happening this time around.
One more thing…
Air temperature doesn’t equal road surface temperature. Even on a cloudy winter day the road surface is going to be warmer than the air temp, often significantly warmer. Take a look at the Rocky Pt. ODOT sensor along Highway 30 in the fog and clouds today. http://www.wrh.noaa.gov/mesowest/getobext.php?sid=ODT95&table=1&banner=off
At 5am, air temp=27, road temp=28.
9am, air temp=28, road=33
11am, air temp=30, road=39
In this case cold rain might lower the road temp a notch or two, but today you wouldn’t have seen freezing rain glazing over the road after 8am or so. At the Enchanted Way sensor south of Salem along I-5 it was 28 at 11am and the road temp was 37. Same thing.
As a result, I don’t believe we’ll have anything other than a spot or two of ice in a valley out near the Coast Range tomorrow morning.
Chief Meteorologist Mark Nelsen