Before we get to the forecast, I want to share a story that came back into my mind while I was banging my head against the desk this morning.
At Penn State, there's a student run organization called Campus Weather Service - there were 3 branches - radio, TV, and newspaper. Since I didn't want to be on-air when I began college, I decided to do the newspaper shift as a freshman. In my first "shift" on Monday nights for "The Collegian", the PSU newspaper, two of my shift-mates were fighting over a degree. I'm sitting there thinking, "Wow, I can't take much more of this bickering over a degree. WHO CARES?!!"
Meanwhile, I've been sitting here for eight hours agonizing over a few degrees. A few degrees difference makes or breaks this forecast. I'm going to do a more thorough model discussion after the Euro comes in, but I'll tell you what I'm thinking.
Scenario A: Temperatures drop to or below freezing around 11pm Tuesday night. Precipitation starts around 1am as ice/snow. If this occurs, I think we'll hold onto frozen precipitation through the entire event - which could mean significant ice and/or snow. If we could be at 28 or 29 after precipitation starts, it should be an all frozen event. We have to see how far the warmth makes it. If it gets into the mid levels of the atmosphere - ice is a MAJOR concern.
The reason I say temperatures shoud drop at or below freezing at 11pm and then have precip start at 1am is because we'll be able to "wet bulb" down to a temperature well below freezing and likely keep the temperature below freezing through the day (though it may rise to 30 or 31). I'm not sure if I've explained wet bulb, but if not, I'll explain this afternoon with the model discussion.
Scenario B: Temperatures drop to or below freezing when precipitation begins around 1am. We hold onto 32 degrees for a while (some snow/ice) and then temperatures rise to about 34 or 35 degrees through the lunch time hour, giving us rain. However, as cold air rushes in behind the storm, we will change back to snow, giving us a chance of some minor accumulation.
Feel free to ask questions - I'll update again around 4pm!