I cringe and shake my head when I see both meteorologists, weather enthusiasts and people who steal images from those folks sharing raw model snow forecast numbers five and six days ahead of a storm. It’s irresponsible at worst and clickbait at best. The science of meteorology and forecasting the atmosphere doesn’t yet have the ability to forecast with useful accuracy snow amounts that far out.

In fact, forecast how much snow falls in a storm is one of the hardest things we do! There are a lot of variables. Sometimes the snow melts when it hits the ground. Sometimes snow that falls will compact as new snow falls on top of it. Sometimes an inch of water falling from a storm does so as 10″ of snow. Sometimes that same inch of water ends up being 20″ or more of snow. It’s a lot to consider.

As I’m writing this Tuesday morning, what CAN and what SHOULD we tell you? I always think it’s just as important for me to tell you what we don’t yet know in addition to what we do know. Here’s a short, not all-inclusive list:

  • I know there will be a strong, high-impact storm moving through the western U.S.
  • I know the storm track has shifted a bit farther north compared to yesterday
  • I know there will be some really heavy snow somewhere in Colorado this weekend
  • I know that there will be travel impacts for the areas that get snow
  • I know the heart of the storm moves in Friday night and Saturday is the most impacted day
  • I don’t know how much snow you’re going to get at your house yet
  • I don’t know where the rain and snow line is going to be on Saturday
  • I don’t know if thunderstorms in Okla/Texas take moisture and reduce upslope flow
  • I don’t know if the storm will keep inching north over the next few days
  • I don’t know if the storm is going to move out slower than we think

Forecasting weather is a process, not a one-time event. There is a reason we come in and do this every day! We’ll learn more about the storm as we begin to launch weather balloons into the eastern fringes of it Tuesday afternoon and get more balloons into it as the rest of the week moves on. We’ll continue to get a better handle on the track as we see how models compare to each other, the trends within them, and how individual models change each time they run.

We also give models small little tweaks and run them more than a dozen times to see how much variability the model sees in the storm. This helps us have a better idea of how much we still don’t know. These multiple model runs are called ensembles…when they contain a wide range of solutions, we know we’ve got less confidence in the forecast. Here’s a couple examples of what types of things we look at behind the scenes:

This image comparison shows a very subtle north shift, of about 40 miles from one computer model from the Monday morning to Monday afternoon model run. A continued trend to the north on the storm path would lower snow amounts over southern Colorado

My main messages for today are that we are getting a better handle and becoming more certain about the timing of the system. You’ve got through the first part of Friday to get things done. We’ll start to go downhill pretty quick from Friday afternoon into Friday night.

I’m also pretty certain that SOMEWHERE in the foothills of Colorado, the mountains between the continental divide and Interstate 25, will get two feet or more of snow. So I do expect some pretty significant impacts from the storm, obviously! I’m not sure if that bullseye will be on the north/northeast slopes of Pikes Peak, I-70 at Idaho Springs or west of Ft. Collins…but we’ll keep working on it!

As of now, I’d plan on not doing much Friday night or Saturday and making necessary plans. I’m hopeful that what I’ve shared here not only increases your understanding of the forecast process and how hard we work for you, but helps calm you – that’s always our goal – not to scare, but to help you prepare.

I’ll keep providing updates over the next few days as we learn more….check back!