And kept the cold air locked up in Canada. By tonight and through the day on Friday that ridge will begin to pull off the coast and allow all that moisture to slide east into the Delaware Valley. By this weekend, the northern branch of the jetstream takes contol and allows cold, dry, air to move back into the east. We often talk about storms. When the flow is from west to east the temperature gradient builds.
Warmer air gets even warmer to the south and colder air gets even colder to the north.
In order to eliminate this tension, a storm takes shape. The counterclockwise wind circulation around the storm moves cold air south and warm air to the north. This returns the atmosphere to it's normal state. As we continue to march through the shortest month of the year, the sun's angle begins to get higher in the sky and temperatures begin to get warmer. The sun heats the ground then the air that comes into contact with the ground becomes warmer.