A lot of folks jumping on the White Christmas bandwagon today, so I’ll begin this post with a word of caution before jumping into the details on what’s shaping up to be an active weather week across the country next week. Despite the excitement, there’s very little confidence in how much snow will fall along the Front Range and eastern Plains next week. It looks likely many across eastern Colorado will see at least two snow chances next week, but how much will fall remains very much in question.
That’s not to say we’re not pulling for a snow (yes, we’ve seen the EURO). In fact, nothing would validate what we’ve been saying for weeks better than the deterministic ECMWF: bitter cold and a good snow to end this otherwise quiet month.
There will be a series of disturbances affecting Colorado as we move into the weekend and next week. Timing and strength of each of these systems have been varying greatly run-to-run in large part due disagreements on what happens when they get east of Colorado. A system due to affect Colorado Sunday and Monday will eventually move into the Great Lakes and deepen. Where this system eventually closes off will greatly affect the eventual track of our end of the week Christmas storm. A lot to watch here.
Models have largely been dismissing our first system due in Monday -- but this one seems like it could sneak up on us. If you’re to believe the 18z GFS, it believes this could be the case too. The image below represents the jet stream location and speed on Monday evening.
As the strong jet stream energy moves over Colorado on Monday, the mountains will get some very heavy snow and wind. East of the mountains, the inevitable snow bands will set up in narrow, but very intense streaks. This far out, it is almost impossible to predict where these “streaks” are going to set up. However, those that do get in those heavier bands will see some good snow. While it’ll be a quick hitting storm, there’s quite a bit of energy with it. We’ll need to watch where models trend with the placement of the jet over the coming days, and also if we do get precipitation Monday, how much of that may at least begin as rain as per the GFS...
The next system will be moving in right on it’s heels Christmas Day. This is the system the EURO has latched onto for a good snow across eastern Colorado, though its ensembles continue to be far less gung-ho here as well. The 18z GFS, which really grabbed onto Monday’s system, is now tracking the surface low too far north of Colorado Christmas Day for much of any snow in Denver, a similar issue we’ve seen with the Canadian. I’m curious to see if the EURO trends to the northern track or stays the course tonight.
There does seem to be enough model consensus at this time to at least introduce a chance for snow Thursday and Friday next week, even with differences in tracks. The EURO has been pretty consistent over the last few days, and it’s ensembles have been showing a pretty good trough digging into the west from the 25-29 for sometime now. Not all models are showing snow on Christmas, however, so a good amount of uncertainty exists.
Where there’s greater confidence is in a good mountain snowfall event over the next week. As we head later into the weekend the flow aloft becomes very favorable for snowfall in the north central mountains. Totals from 1 - 2 feet will certainly be possible through Sunday through Monday, with more snow likely as we head into the middle of next week.
Here’s the current 5-day snowfall forecast from FreshyMap:
Cold, cold, cold?
Next week is forecast to get progressively colder as we go, and all indications are the cold sticks with us into the New Year. Here’s today’s 12z GEM 850 hpa mean temperature ensemble control run for 12z Dec 29, and it’s mean ensemble run below.