Monday, December 13, 2010
Ice This Week?
The above image is BUFKIT showing the latest GFS model run. The timebar goes from right to left (you guys should know that by now). Anywho, it shows some icing through the day on Wednesday, as indicated by the red bars. The red line is the temperature and I have made a "freezing line" in light blue.
The GFS does have us at or below freezing as the precipitation moves in. This would lead to some light icing if this happened. Two things to note. First, models have a hard time handling shallow cold air. (I'll explain shallow cold air shortly) Second, notice the big gap between the green and red line. That is the difference between the temperature and dewpoint, which indicates dry air ahead of this system. This should lead to some "evaporative cooling". Lick the back of you hand. Go ahead... it's cleaner than the palm of your hand! Now, blow on it. Colder?? That's evaporative cooling.
Now, what do I mean when I say "shallow cold air"? Below is a forecast Skew T of the GFS model...
For it to be snow, the entire column of air would need to be at or close to 32.
Posted By: Ryan at 11:19 AM