Here’s a nice image that displays the challenges of the long term forecast. It’s the various GFS ensemble members for Tuesday, December 8th (D+8 forecast). A bit of confusion eh?
Okay, back at it this evening. I just perused the 00z maps to compare with the last 24 hours. There had been quite a bit of excitement with various models (Canadian and GFS) showing arctic air intrusions into the Pacific Northwest at differing time periods. Of course each model run has been different. Notice the spaghetti chart is a huge mess from the 12z GFS. That’s unusually messy for Day 8. Now the 00z models are in and I don’t see any sign of a big blast of cold air; that’s due to models showing the upper level ridge staying quite close to the Coast. What I do see is classic El Nino conditions. High pressure nearby, a wet southerly jet across the USA, and cool offshore flow for more than half the 7 day forecast here in the Pacific Northwest. Since the first week of December is just around the corner, any offshore flow will keep us chilly. It’s tough to get high temps above about 52 at PDX with easterly flow December through January. More likely in the 45-50 degree range later next week. Add to that overnight lows down in the 20s in outlying areas and it’s going to really feel like December around here as we progress through the next 7-10 days.
Chief Meteorologist Mark Nelsen