Pre-Christmas weather pattern looks active

Lots of buzz about the pattern change for the Dec 20-24 time period, which is looking more and more likely. It’s one thing to be confidence in a stormy pattern and quite another to even entertain specifics of wintry weather when we are still in the 7-14 day time frame. Here’s what we know right now and more importantly what we don’t know.

The storm track gets active in the Southeast:

Both the ECMWF and GFS models show lower pressures over the Southeast in this time frame which would mean some kind of low pressure in the vicinity. Even a few days ahead the track would be hard to pin down let alone 7-10 days out. Then the cold air issues. Which is always an issue but even at this time range it looks really marginal.

GFS Model:

Be cautious of what you are looking at!

Always be cautious of the ECMWF snowfall plots. I’ve seen quite a few people post these and not really look at the thicknesses and temperatures. The thing about the WECMWF snowfall maps they take all wintry weather in the model and convert it to snow at a 10:1 ratio. So even if you have a rain/snow mix or a freezing rain or sleet mix the model makes it all snow at a 10:1 ratio of liquid to snow. In my opinion, this would be a wintry mix issue so the snow totals you see in the ECMWF are almost always overdone, let alone at 7-10 days if it will even happen.

Plus let’s remember on the error on long-range snowfall forecast in general. Don’t get caught up in a wishcast of a 1-10% chance of something happening and ignore the 90% chance it won’t happen. As we get close once confidence gets above 30% at 7 days we start getting serious and as confidence grows to 50% and above then we start talking possible totals.