12/6/21 Monday 4 am
I wasn’t sleeping, I am not sure if it was some of the horrible football games yesterday, or just my overall anxiety level with the second storm coming in on Thursday. Either way, I decided to get an early start to today’s updates. Regarding that second storm, I am relatively confident we will get 1 to 2 feet of snow at the local resorts. I am less confident about what will happen in the lower elevations and southern portions of the border counties. I will talk more about the second storm in my next update later today.
We are taught in many facets of our lives to go from general to specific. Interpreting weather modeling is similar. People ask me how I choose the particular models I do. The answer is it depends on how far away the storm is. I talk a lot about the ensemble (family) models from the Euro and GFS. I don’t talk as much about the Canadian ensembles, but I do look at them. The good thing about the ensembles is, depending on which family you choose, you can see up to 51 versions of that model family. You can look at the individual runs or you can look at the average of those runs. This is referred to as the ensemble mean and it is what most forecasters look at. Sometimes they are referred to as clusters, it just depends on which parameter you are looking at.
The only problem with the ensembles is they are very low resolution. This becomes a problem where we live because of the elevation changes. They will spread out the higher precipitation over miles. The individual versions of the models are called the deterministic runs. They are sometimes referred to as the operational version of the model. These are the ones I usually post–the Euro, Canadian, and GFS. These models are medium-resolution models. Out of the three, the Euro has the highest resolution and the Canadian has the lowest. However, they all are higher than the ensembles.
Back to general to specific, I consider the lowest resolution models (the ensembles) to be the general. I look at the ensemble models for trends and verification of the individual models. As the storm gets closer I lean more on the medium-resolution operational models. Within 24 hours of the storm, I start to look at higher resolution models.
High-resolution models are not always the most accurate. One thing they are good for in the winter is smaller storms. Compared to what we hope is coming on Thursday and Friday, tonight is a relatively small storm. I have been relying upon the higher resolution models for my forecast for this first storm.
The one thing about the high-resolution models that I have access to is that they are all NOAA-based. One is an operational model, the NAM 3km model. The others are all blended models and are slightly higher resolution than the NAM 3km. They are the NDFD 2.5km, the WPC 2.5km, and the NBM 2.5km. Don’t worry, there is no test at the end.
So here they are, showing the liquid-equivalent precipitation. To convert this to snow at the resorts multiply times 12. For pass level or upper mountain, multiply times 13. Again, this is for tonight through late Tuesday only.
WPC 2.5 km
NBM 2.5 km
NDFD 2.5 km
Here is my adjusted forecast.
The highest accumulations will fall from Telluride to Red Mountain. 4 to 6 inches of snow is possible there with higher amounts possible on the upper mountains. 2 to 4 inches looks good for Silverton (in town) and Rico. Purgatory and Wolf Creek will likely get 2 to 3 inches at most. In the lower and mid-elevations 0 to 2 inches could fall before melting.
As I was finishing up this post, I noticed that while I was writing it, the NWS went ahead and issued an advisory for the Northwest San Juans. It looks like they are a little more enthusiastic than I am with their forecast. For now, I will stick with where I am at and revisit this in my noon update.
Here is their Winter Weather Advisory
URGENT – WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
205 AM MST MON DEC 6 2021
NORTHWEST SAN JUAN MOUNTAINS-
INCLUDING THE CITIES OF TELLURIDE, OURAY, AND LAKE CITY
205 AM MST MON DEC 6 2021
…WINTER WEATHER ADVISORY IN EFFECT FROM 11 PM THIS EVENING TO NOON MST TUESDAY…
* WHAT…SNOW. TOTAL SNOW ACCUMULATIONS OF 4 TO 8 INCHES WITH THE GREATEST ACCUMULATIONS EXPECTED ABOVE 10,000 FEET. WINDS GUSTING AS HIGH AS 40 MPH.
* WHERE…NORTHWEST SAN JUAN MOUNTAINS.
* WHEN…FROM 11 PM THIS EVENING TO NOON MST TUESDAY.
* IMPACTS…TRAVEL COULD BE VERY DIFFICULT. PATCHY BLOWING SNOW COULD SIGNIFICANTLY REDUCE VISIBILITY.
My next update will be out around noon. Thanks for following and supporting the site!