It seems obvious that once a cold front passes the temperatures will decrease. There are cases though where a front will be labeled a cold front even though the temperatures rise behind it. This event will be most pronounced at night when the skies are clear with light winds ahead of the cold front and the skies are cloudy and winds pick up behind the cold front. Ahead of the cold front the temperatures cool by radiational cooling. The clear skies and light winds allows significant cooling. Since the wind behind the cold front is stronger the air is more mixed. Clouds behind the cold front can also limit the amount of radiational cooling behind the cold front. Because radiational cooling is not as much behind the cold front, the strong radiational cooling ahead of the cold front can cause temperatures to be cooler ahead of the front. For example, it may be 25 F at 3 am with clear skies and calm wind, then the cold front passes and it is 28 F at 5 am with partly cloudy skies and winds out of the north at 10 miles per hour. Look for this situation to happen. It is not as uncommon as you may think. |