Today’s models are increasingly insistent that a sharp (but brief) change towards colder weather is likely starting Sunday. Temperatures at 5,000 feet (850 mb) are expected to drop to around -5 C (lower 20s in F) by Monday morning. The NAM model is the coldest, with the GFS and ECMWF not quite as chilly.
As the cold front passes through Sunday morning, a brief round of light rain is possible. The front is quite moisture-starved, so there may be locations that don’t record any measureable rain. Later Sunday, colder air begins surging into the area from the north and northwest — you’ll notice the colder breeze (10-20 mph with higher gusts) in the afternoon and evening. Sunday night could be the coldest night since last winter. I expect PDX to drop into the mid 30s, with some upper 20s possible in the typical cold spots (Hillsboro, Forest Grove, Battle Ground, Scappoose).
The East Wind picks up Monday… and for the first time this fall, it should be a cold wind (past east wind events this month have been warm). If the wind calms down Monday night, it could be very chilly… so we’ll have to see what the wind does as time gets closer before we’ll know how cold it might be.
East of the Cascades will be even colder — highs in the 40s and lows in the teens are likely Monday and Tuesday.
It looks like a significant pattern change will occur mid-late next week. From cold and dry… to mild and wet. Several days of rain are possible beginning Thursday… and strong south winds could buffet the coast as deep lows wind up offshore.
The "boring" weather season may indeed be behind us…
– Drew J