Flurries ended soon after sunset and now cold and dry air is pouring into the area.
Models are a mess this evening; thus we have a very challenging Thursday-Sunday forecast. What seemed like a very clear “moisture returns and rides over the cold air Saturday” event is now something a bit different. It appears the arctic boundary (dividing line between cold and dry air and milder air) will sit across central/southern Oregon the next few days. Several surface lows and/or weak disturbances in the upper atmosphere will ride along that boundary Thursday and Friday. Then the stronger warm front finally swings north (probably) on Saturday. Depending on which model and which run you look at, each of those waves of moisture could bring snow to parts of the Willamette Valley. As of now our RPM and GFS don’t really bring much of anything to the Portland area until late Friday night. The new 00z ECMWF looks similar, so our forecast is staying that way. Of course it’s only late Tuesday and I’m pretty sure with the boundary so close to us that things will change.
I am very confident that we’re not getting out of the cold air until at least Sunday. The 00z GFS and 00z ECMWF don’t have any southerly wind in the metro area through Saturday. Anyone that thinks they can predict snow totals for Saturday, on a Tuesday evening, in a pattern like this, is nuts!
More tomorrow…enjoy the fresh Canadian air and wind tomorrow!
Chief Meteorologist Mark Nelsen