The active weather pattern will continue around WNC for the foreseeable future beginning today with rain and then Northwest flownsnowfall for some late tonight & into tomorrow. Locations above 3500’ have the chance to see a couple of snow showers, with even a dusting to 2” possible above 4500’. That is not really the storm I am focusing on though, but i’ll begin this article there. Models continue to suggest that as an Upper Level Low progresses over WNC tonight, that snow showers will be possible in similar areas that saw snow on Monday. So don’t be surprised if you live North of I-40 tomorrow morning and wake up to a dusting of snowfall. Check out the most recent Nam3km Precipitation Depiction below for tonight.

My attention has turned to a weak Gulf Low that will meander up the East Coast late Sunday and into Monday. Overrunning precipitation could collide with an Upper Level Low, and a zone of convergence will setup over WNC. Taking advantage of the cold air provided by the Upper Level Low, moisture could very well fall in the form of snowfall for most. This would even include valley locations down to around 1700’. There is still a lot of information to be proceed, but lets look over the details as I explain why I think snowfall will be possible.

Model Data

The most recent NAM model continues to show a similar overrunning precipitation event late Sunday and into Monday around WNC. Below you can see a simulation of the most recent model run, and where it depicts precipitation to occur. Snowfall totals will be tough to nail down until 12-24 hours out from this event, but I have also shown what the most recent NAM depicted regarding those numbers.

Model Comparison

So when forecasting event such as what will arrive late Sunday night, I dig very deep into the data. What I am finding is that most models have a very saturated column aloft over WNC late Sunday and into Monday, with near frozen temperatures in place. As a baroclinic zone develops between the Upper Level Low and the surface low, snowfall develops over WNC. This is considered overrunning precipitation. It is notoriously poorly modeled, and is typically where our surprise snowstorms come from. Lets take a look below at what the most recent GFS Model is depicting.

Now let’s compare that what what the 0z European model showed occurring. When evaluating these systems coming in, I like to favor the GFS in upslope events because it tends to do better with their progression. The Euro struggles to resolve the low end moisture returns and that causes its output to be minimal. What happens in actuality most of the time is that the Euro plays catchup to the GFS in these events. So below you see how the Euro has all the same players on the field, just doesn’t show that weak precipitation over WNC.

Conclusion

What this all boils down to is agreement. One thing that the models are in agreement of is interaction between the surface low and the Upper Level Low. That will correlate to moisture development over WNC. With a column very close to freezing, there is potential for a low end winter event early Monday morning and through the day on Monday. Depending on how heavy the precipitation is, will determine how much snow falls. I have seen these type of overrunning events bring 3”+ of snow to isolated valley locations. That doesn’t mean it will occur this time, but the potential is there. Check back with me soon as I continue to digest data to give you the most accurate forecast!