4:20 PM, MDT, December 12, 2017
A cold front and upper level disturbance on Wednesday evening will likely have a bigger impact along the Front Range than what we were thinking as recently as yesterday. Accumulating snow (probably minor) is appearing likely in and along the mountains with less chance farther east. The timing is Wednesday evening through early Thursday. So, nothing big appears on the way, but it may very well be something different than what we have had lately. I will update tomorrow.
Friday, December 1, 2017, 11:15 AM
Expect a mild, dry weekend with above average temperatures and possibly a bit breezy at times. A cold front overnight Sunday into early Monday will make the early part of next week more like December. Over the last few days it was appearing that the cold front would bring a snowfall with it on Monday. Although that still looks like a possibility, the magnitude is looking rather minor. I will update Sunday if there are major changes.
La Nina this winter
The Pacific Ocean is in a La Nina pattern this winter, with below average sea surface temperatures in the eastern Tropical Pacific. Although there is always a lot of talk about what it means for our winter season, the truth is that the El Nino-La Nina phases are important influences but they don’t act alone. For that reason there can be a lot of variability from one season to the next. The general expectation is for wetter/snowier in the Pacific Northwest and northern Rockies, and drier for the Southwest and southern Rockies. Colorado is often in between these two tendencies. But more often than not the Front Range east slope region and eastern Colorado run on the dry side during La Nina. The West Slope is more uncertain with the best chances for a snowy winter in the northwestern and north central part of Colorado.
Although the snow pattern is somewhat uncertain, there appears to be a much stronger correlation between La Nina and downslope windstorms. So be prepared for frequent visits from Chinook winds.