Well this has been nice. The last two days in the Pacific Northwest, including the Columbia River Gorge and the Portland Metro, have had just about the most beautiful weather you can hope for in November: mostly clear skies and not a drop of rain to be seen. And we have at least another 5-6 days of mostly dry conditions on the way. Tomorrow Friday afternoon, there might be a few passing sprinkles as a very weak system brushes by to our north. But then it turns totally dry again for Saturday-Tuesday as the West Coast Ridge strengthens.

The one caveat – almost inevitable at this point in the season – will be the temperatures. Someone who’s not an expert on Northwest seasonal weather may think, “it’s going to be sunny with dry offshore flow, and we’re normally in the 50s at this time of year, even with all the clouds. I bet it gets up to 62 or even 65 with all that sunshine!” Sad to say, it usually doesn’t work like that in November. Now, California doesn’t have this same kind of problem, at least not yet: Conditions there today were warm and dry enough to start another serious wildfire, on the east side of the Sacramento Valley. The south coast will likely be in a ‘Santa Ana’ pattern this weekend, with dry east wind and temps well into the 80s.

Even Brookings can hit 70 degrees in this kind of pattern, if a dry NE wind comes down from the coastal mountains. This might happen Sunday; we will have to wait and see. But the rest of the Northwest is too far north to see any kind of warmth from ridging, once you get past Halloween. The weak sun and long nights allow cool air to quickly accumulate in the lowlands; even if the mid-level airmass manages to turn warm, it just creates a hazy/foggy inversion layer. (Up in the Cascades, it’s a different ball game though.) In the particular pattern we have on tap, there will be cold, wintry airmasses just about everywhere east of the Rockies. That sure doesn’t help us when it comes to getting warm with offshore flow!

In fact the best pattern for mild/warm temps in November, is actually westerly/southwesterly flow riding over the top of a weak ridge to our south.  That’s the pattern we had at the start of the month that got us into the upper 60s for a couple days.

Today’s temps in The Dalles were a stark reminder that winter really isn’t very far off: a morning low of 26 followed by an afternoon high of 53. Drop that high temp another 10 degrees, and we’re there. The Portland Metro was just a couple degrees warmer today, though patchy fog last night held low temps up in some areas.

This is the 850mb airmass temperature forecast for 4pm Sunday afternoon. The boundary between blue and light green, represents temps of 0 degrees Celsius. Notice how Eastern Washington and Oregon stay under relatively cool air in this kind of offshore pattern. I doubt we get much above 50 degrees in the Gorge, assuming this is true.

The mid-level airmass will be significantly warmer west of the Cascades, but even there you have to be careful: Inversions can still trap cool air in the lowlands. Furthermore, the strong east winds in Portland will be coming through the Gorge, originating from the cool airmass on the east side. It is unusual to get downslope warming effects from east wind, this late in the season. The wind in Portland is instead a low-level gap wind, coming almost entirely from cool air in the Columbia Gorge.

If…and it’s a big if…Portland manages to get a little bit of downslope warming in the area (not likely, but always possible) – then some locations MIGHT sneak up into the low 60s, next Sunday or Monday. That much is not out of the question. Far more likely, however, is something in the 55-59 degree range, and probably a few degrees cooler in and near the Gorge. And more cold nights for places like Hood River and The Dalles.

Sorry folks, but that’s the way it is in the 2nd week of November. We would probably have better luck, temperature-wise, with a big ridge in late February than we would now. By then the sun angle is once again getting pretty strong, about on par with mid-October.

In any case…enjoy the dry weather and sunshine these next few days!