Real slow weather pattern continues. If the action doesn’t pick up in the next 2 weeks or so, I think it’s fair to say that this winter will go down as just about the deadest for weather enthusiasts in 10 years.
The main issue since Christmas (the last time we had interesting weather) is a persistent upper-level ridge either over us, just to our west, or just to our east. That weakens any storms that approach from the west or blocks them completely. Quite a bit of our precipitation has been from the pattern coming up the next 3 days; onshore flow at the low levels bringing in lots of steady light rain in the valleys and steady light snow in the Cascades. When the upper level ridge is just to our west, the surface high is offshore too, thus the onshore westerly and moist flow. It’s wettest on the east side of the Willamette Valley and west slopes of the Cascades and Coast Range in this pattern too; like we saw a couple of weeks ago. Here’s the 3 day rainfall forecast from our 00z RPM:
We do finally get a couple of cold upper level troughs through here over the next 8-9 days. The first is later Saturday and early Sunday. This one brings sticking snow down around 1,500′ or so, but not a ton of moisture. Then next Monday night and Tuesday a 2nd and maybe colder trough drops in. Several models have been pushing 850mb temps down around that magic -7 degree temp, that’s what we like to see to get a chance of sticking snow down to the Valley floor. But even with that everything else has to work out perfectly (precipitation intensity, no mixing wind, overnight hours etc…). There is a hint on the ECMWF and now the 00z GFS that these troughs may split a bit. Yes, the dreaded splitty flow. This can be a big issue for getting decent precipitation and of course snow to lower elevations. We’ll see how this all pans out.
For now it should suffice to say there is just a chance that we’ll see sticking snow lower than 1,000′ about 8 days away.
Beyond that? Look at the 00z GFS 850mb ensemble temperature chart. Pretty decent agreement on slightly warmer temps beyond next Tuesday for a few days. Then wide variation with some members (and the operational run) showing another brush with low elevation snow right around the 25th/26th:
The new 00z ECMWF is out, or at least most of it. Here’s the 500mb chart for next Tuesday:
and the matching 500-1000mb thickness/precip map:
Chief Meteorologist Mark Nelsen