Accumulating snow possible in Twin Cities next week
Fall 2022 will end quite mild – at nearly 2 degrees above normal – but we have certainly had some snow and at least short bursts of cold. Believe it or not, despite the white coating for the last couple of weeks the Twin Cities is below normal for autumn snowfall by 0.6 inches. At least for now. A storm system in the last 36 hours of meteorological fall could change that.
Our storm system, or at least the beginnings of it, is still way out in the north Pacific, near the Aleutians. This means a lot can happen before it arrives in the middle of America, but most of the models have locked onto a similar solution.
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The problem with a storm systems like this, early in the season, is that 50 to 100 miles north or south can make a big difference in totals. Right now the European and American models are nearly 200 miles apart on their forecast track Tuesday afternoon.
The difference is rain (European) or heavy snow (American) for southeastern Minnesota. Most of the models do keep the Twin Cities in all snow, but we want to be on that sweet spot of the narrow, heavy band that develops just to the northwest of the rain area.
There will be ample moisture available as the Gulf opens up ahead of the main upper-level wave early in the week. In fact, the European model is forecasting 2 sigma precipitable water values Tuesday afternoon, based on 1991-2020 climatology. That means moisture content in the top 2% for the time of year.
Ninety-six hours is a little early to get too precise with snow totals, but the models are in pretty good agreement on the general area of snow, though amounts differ.
The GFS (American model) is the least aggressive on snow right now with its track more south than the other models.
The key is to look at the ensembles of the models. Remember, the ensembles are running the deterministic models (European, American (GFS), Canadian (GEM)) many different times with tweaked scenarios, or what we call perturbations, using different conditions to see how touchy a particular solution is. The basic idea is that you average these together and in theory, have a more solid solution. When we look at the American (GFS) model’s ensembles, we get a snowfall track that’s more in line with the other models and the other ensembles, so it appears the GFS's individual runs right now may be less reliable.
Either way, this does not look like a terribly big storm but even a few inches will be enough to make this a snowier than normal fall, and could set the stage for the start of winter if we can get cold air to settle in behind it.
Here are the latest probabilities for the Twin Cities (by inches) based on all the models.
The most likely range for the Twin Cities is in the 2 to 4 inches, but again this could certainly shift. I know we sound like a broken record this time of year, but every day we get closer with more data on the storm we're able to refine the forecast as the storm gets closer.
