UPDATE 7:15 PM, 12/17: My “few mountain snow showers” below has arrived as a mix of rain and snow, fairly heavy at times, this evening as the cold front pushes in. Some spots especially at 2,000 feet or higher elevation may get enough snow for some accumulation. END UPDATE
A week that will start chilly will flip by the end of the week, when 60s and maybe even some low 70s will be possible. We’re still experiencing the windy chill behind the last cold front, and there will be a reinforcing shot on Tuesday, keeping us in 40s highs/20s-low 30s lows temperatures through midweek. But then late week, the pattern reorganizes a bit to focus low-pressure troughing into the southwestern U.S., and that in turn will tilt the mid and upper level wind flow from southwest to northeast across the eastern two-thirds of the nation. That will bring in significantly milder weather for Thursday through Saturday. The low in the Southwest will eventually trigger a significant storm system that will track from the central U.S. toward the Great Lakes, ultimately pulling another cold front through next weekend to bring an end to the mild spell and likely return us to colder weather for Christmas week. The week’s seesawing temperature are vividly shown on the European model, which shows our region in the bluer colors on Tuesday, for below-normal temperatures behind the next reinforcing cold front, and then in yellow and brown colors for above-normal temperatures by Saturday. Little or no rain is expected during the work week — I wouldn’t rule out a few mountain snow showers with the next frontal passage Tuesday. Rain will return ahead of the cold front this weekend. Prospects for temperature levels (colder, but how much so?) and moisture-bearing systems are a bit uncertain for Christmas week. We’ll look at that more in detail later this week.