October will end cooler than average for most of us in the region. The temperature at PDX (53.5) will end up the coolest in 5 years. Eugene will be the coolest since 1981. Of course all that sunny weather means only about 1/2 of our normal rainfall.
Now November is our wettest month of the year on average here in Portland…5.63″ is the average. And in accordance with that we get a much wetter weather pattern once we get past the 1st day of the month.
Several items of interest. First is the surface low pressure system that tracks into the Strait of Juan de Fuca Saturday. Models have slowed it down a bit, and the 00z GFS has pushed it a little farther south. Still, gusts shouldn’t get much above 60 mph on the northern Oregon Coast and 35-45 mph here in the valleys. It WILL be the strongest storm we’ve seen in a month though. Wind should pick up nicely just before daybreak Saturday here in the Portland area.
Here’s the 00z WRF-GFS showing the low inland over Washington and the tight southerly pressure gradient:
Then, behind the cold front, strong and cold westerly flow behind the cold front will push a continuous stream of snow into the Cascades through sometime Sunday. This will be the first dump of snow down to below pass elevations so far this season. Government Camp could easily see 6-10″ from midday Saturday through midday Sunday. A good 10-15″ more likely higher up in the mountains. Watch out travelling through the Cascades from near sunset Saturday through midday Sunday; expect mid-winter driving conditions!
Another system comes through Monday afternoon through Tuesday, but snow levels will be rising to around 6,000′ briefly. Then snow levels fall again the 2nd half of next week. So the snow this weekend will be sticking around and we’ll see additional base accumulations next week. Maybe most important is that we don’t see any sign of significantly warmer weather in the long-range.
Take a look at the 00z GFS ensemble chart:
and the 12z ECMWF ensemble chart:
Both show atmospheric temperatures over our area well below average through most of the foreseeable future (after tomorrow). By the way, those of you planning to get on the “Wishcast Express”? Based on the 00z operational GFS it appears to be cold enough for snow in Portland about 11 days from now. But note the operational run was an outlier, the average of the ensembles is significantly warmer, but still below average. We’ll see…
Chief Meteorologist Mark Nelsen