That was a fun little 1/2 hour snowstorm that moved through the metro area between 7-8pm. Proves that precipitation intensity is often more important than the actual freezing level. We watched the Sylvan ODOT camera (at 700′) for about 15 minutes and it went from bare to at least 1/2 inch with a snow-covered road in just that time. Once the showers moved off to the north the roadway melted nicely. Now it’s going to be dry until sometime late tonight. With any clearing there will be quite a bit of ice on the roadways.
Quite a tricky forecast for the next 18 hours or so. Beautiful wrapped up surface low has suddenly deepended west of Newport and at 8:30pm is out around 128W. I noticed earlier today as the low passed near Buoy 46005, temperatures on the buoy dropped to the 36-38 degree range. That is very cold for sitting on a little floating buoy in the middle of a 50 degree ocean.
Both versions of the MM5 model now move the low a bit farther north as it moves inland tomorrow morning/midday. They move it directly over Portland! They also agree on a pretty good slug of precipitation beginning by 5-6 am at the latest, maybe by 3am. If so, this could easily be snow since we have cool easterly flow moving out of the Gorge as the low approaches. IF everything was perfect, we could get a 3-5" wet/heavy snowfall out of this for the morning commute down to the valley floor. BUT, it looks slightly too warm for that. So two thoughts stick out in my mind.
1. With the low track farther north, sea-level or valley-floor snow is unlikely south of Portland and south of Tillamook. Looks like Astoria-Tillamook and Longview-Portland is the most likely spot for significant snow down to the lowest elevations. Apparently this is the winter for coastal snowfall.
2. That said, it is a bit warmer than I would like to see at the lowest levels to call for a snow storm in Portland. And by that I mean by maybe only 2-3 degrees too warm. It’s going to be close!
–Trace-2" possible at the lowest elevations from Chehalis to Wilsonville AND Tillamook north to Long Beach Peninsula
–2-3" on the hills above 500′ and possibly at the coastline if the precip is heavy enough.
–3-5" up around 1000′ or higher.
–It’s quite possible that we have a messy morning commute coming. A few inches at/above 500′ affects quite a few people.
Once the precip lets up around midday tomorrow, temps should rise up to the lower 40’s. Then with stronger onshore flow Wednesday and Thursday AM, it’s unlikely that we’ll see significant snow to such a low elevation. I think it’s possible this will be our last good threat for snow this season, since next week should be quite a bit milder…Mark