There is a chance for showers and isolated downpours Tuesday night into Wednesday (12/30 to 12/31). This will be a cold system, so snow levels could drop as low as 2000-3000 feet. Right now it looks like moisture availability will be limited, so rain/snow amounts will only be light/moderate.
We are in a unique pattern where the storm track is highly amplified. It goes all the way up into the Gulf of Alaska and straight down into the West Coast and Rockies. Our next storm system will be taking this track. You can spot it on the 500 mb maps below.
All computer forecasts have this system moving into our area, so there is high confidence that this will happen. However, whenever a storm takes a track like this, it is tough to pick up any moisture. This could significantly inhibit rainfall/snowfall totals.
With the core of the system passing overhead on Wednesday, the atmosphere will become unstable. This will bring convection, which means we could see isolated downpours, possibly even a rumble or two of thunder. The air aloft will be so cold, I can't rule out some small hail as well.
Snow levels will continue to drop as this system approaches. By Wednesday, snow levels will drop as low as 2,000-3,000 feet.
Again, there is still a lot of uncertainty with the forecast, so I wouldn't get too excited yet. A lot of times storm systems like this can be a lot of bark with little bite. It will all depend on the track of this system. If it is deeper and more westerly, then it will tap into more moisture. However, right now there is no data supporting a westerly track.
One thing is certain with this storm: it will turn colder 12/31 into 1/1.