11/08/26 2:30pm: Hi, I hope you are having a great weekend (Go Broncos, another wild win!).

It's another really warm Sunday after a warm Saturday. It's currently 68 at my house in Westminster (after a high here of 69 yesterday, officially 65 yesterday for Denver at the airport and 60 on Friday). Enjoy this nice and warm weather over the next 6-7 days because there are signs of colder and more active weather on the horizon.

I know folks are skeptical, but one thing to remember is that it is very early in the cold-season, really we are just getting started. And the main winter jet-stream pattern has not been established yet. Yes we have had some storms but its been intermittent and common during the fall transition. It's still early November and we have most of the winter season in front of us (remember it snowed in May last years, so we have a long way to go).

In terms of the outlook over the next several weeks to months.

First, we will have to get through this warm and dry pattern for the next 7-days or so. From today through next Saturday (11/08-11/15). Dry and sunny conditions, some wind at times, especially in the mountains.

Better to look at the ensemble models beyond 5 days out as they show a spread of solutions across a bunch of similar models. The ensemble models (like the ECMWF Ensemble) show the first set of colder storms (especially for the mountains) around Nov 16th-22nd. You can see this on image2: showing the Total Snowfall Plumes for Vail Pass (more snow after 11/16).

It also looks colder for the front-rang (Den/Bou) as well after Nov 16th but its unclear if we get any snow initially. Hard to gauge any details right now: but overall a better chance for some snow and turning colder. Mountains will have best chances for snow 11/16-11/22.

You can also see this precip pattern change in the 8-14 day outlook below (although it's still showing warmer initially). But great to see above average precip chances for all of CO, favoring southern CO for the highest chances.

Finally, I’m seeing signs in the longer range climate models (like ECMWF seasonal) and also the CFSv2 seasonal model that we are potentially in for a much colder December and possible colder than normal extending into parts of Jan and Feb (that's what the longer range seasonal models are showing). The first 2 weeks in Dec looks interesting but who knows.

Part of this is related to the models showing some sudden stratospheric warming (SSW) near the Polar Vortex. SSW can weaken the polar vortex and favor a negative Arctic Oscillation, which is essentially a weakness in the Polar Jet Stream and allows for much colder air to dive south into Canada and parts of the U.S.

So there is some indication of much colder / Arctic air moving into the U.S. by early Dec…it is unclear where the coldest air comes in, it could be east of Colorado (biggest impacts of a negative A.O. polar vortex air is usually east of the Mississippi)

So there is potential for an active storm track with much colder air in December but the details and impacts for CO are uncertain. Just something to watch and gives me hope (in light of this warm and dry start for northern CO).

Anyway, that is all for now. Nothing we can do about the warm weather, other than go outside and enjoy it (which I’m going to do now 🙂. Stoked on the Broncos as well!

First image is the latest 8-14 day outlook from NOAA / NCEP. Second image is the Snow Plume forecast for Vail. Third image loop show the rolling 7-day air-T forecast anomalies from now through mid-Dec (you can see the red turn to blue over CO). Last image shows T anomalies for Feb from the ECMWF seasonal model, we shall see.