The forecast is still on track for a Trace-3″ across the lowest elevations of the Portland metro area by Monday morning, with almost all of that sticking AFTER 7pm tonight. BUT, the chance for someone to get really dumped on far west metro or up north toward Longview seems to have increased from what I saw at midnight. Here’s the latest snow accumulation forecast from HRRR model. A pretty good representation of what I think is most likely to happen between now and the Monday AM commute:
Notice the heavier totals west and north metro and far less south and east where we’ll stay as rain or rain/snow mix before a late evening switchover.
As expected the airmass over us has cooled off and many are seeing a rain/snow mix in the lowlands. Here at 1,000′ I’ve had mainly snow the past 2 hours, but it was sticking better an hour ago and now I’m getting more rain than snow. I do see the warmer air is moving in aloft in the SE metro area with the sticking snow level up around 4,000′ just SE of Estacada on Wanderer’s Peak. Yet at 1,000′ in the Coast Range it’s snowing like crazy. That’s the effect of a stationary front sitting over our region; warmer south and east and colder north and west.
We’ve now seen the last of the model runs before this event. The last-minute “wrinkle” is that they are all slightly farther south with the surface low pressure that tracks through the region this evening. The ECMWF decided to move the low much farther south and now brings it just south of PDX around 10pm. This is what I mentioned in the posting yesterday evening that “could go wrong”. In this case that opens up the possibility that some locations in the far west or north metro (Forest Grove, Banks, Vernonia, St. Helens, Woodland) could get totally dumped on with snow this evening. The ECMWF itself shows that possibility, although a bit extreme…a foot+ snow out near the Coast Range and north:
The resolution of the model leads to some contouring issues here, but you get the idea…loads of snow possible far west and north metro. We’ll see how this plays out, is it really going to be a “Trace-15” in the metro area? That sounds familiar…but could happen.
Flooding may be in issue this afternoon/evening as well with the heavy rain sitting directly over the Portland metro area. Assuming it all falls as rain south and east metro through the evening, check out the forecast from the HRRR!
That will cause some urban flooding and creeks surge out of their banks. I’ll be keeping a close eye on that this afternoon too.
I’ll be doing some live Facebook videos later once I get settled in and the Super Bowl is on, then we’ll be on the air much of the time from 8:30-11pm tonight on FOX12.
Chief Meteorologist Mark Nelsen