Wanted to take a moment to share some images that help to highlight the impressiveness of the incoming cold front. Over the last 24 hours we have gone from temps in the teens and twenties with a heavy 3-7 inch region wide snowfall that ended as freezing rain as the upper atmosphere warmed from the top down. By yesterday evening it was some 5-10 degrees warmer at the highest elevations of the Catskill Mountains then it was down in the valley locations. Basically a text book example of warming aloft and CAD at the surface, which stands for cold air damming. Remember cold air is denser and heavier, it naturally seeks the lowest point, like opening the freezing and putting you hand down at the floor, throw in some fresh snow pack and its like dropping ice cubes in your drink, in this case your sipping on the atmosphere.
As the warm air came in from the south it went up and over the cold air at the surface, over the course of the day it very slowly started to erode the cold air from the top down, hence the warmer temps on the mountain peaks. This process was actually expedited once the heavy rain moved into the region, why? Because the precipitation actually helps transfer the warmer air aloft and mix it down to the surface. Due to the extreme temperature gradient we also saw some imbedded thunderstorms associated with the front early this morning, Ive seen some posts describing how loud the thunder was. If you thought it sounded loader than usual, guess what? Your right.. When you have warmer air on top of colder air as we did this morning, that is known as a temperature inversion, the thunderstorms that formed were elevated, they needed to form in the warmer air in the upper atmosphere. When the lightning struck the surface its sound waves were trapped by the temp inversion, basically the atmosphere had better acoustics than usual. In the summer, storms from near the surface, the sound of the lightning strike is sent off in all directions and loses its acoustic strength rather quickly. So basically nature but on a winter concert last night, in and atmospheric amphitheater and had the bass all the way up.
Now about that cold front, here is the surface temps at 11am, then at 2PM,6PM and finally at 3AM. You can can clearly see the cold front slamming in from the NW to the SE. Not only will this turn the remaining water logged snowpack into something more the consistency of a glacier, but it will lead to the frozen door lock, black ice, rapid freeze up we all dread so much. Please use caution overnight, and be prepared for vastly different conditions by tomorrow AM. Remember, if you don’t like Hudson Valley Weather, wait 30 minutes….