Fall is a time of year when we often experience big temperature swings, and this weekend is no exception.  Recent temperatures have been unseasonably warm, but big changes are taking place, and you'll really feel the difference on Sunday.  A cold front moved through Saturday afternoon, and behind the front will be significantly cooler air with most of Sunday spent near 50 degrees.  Not only will Sunday be about twenty degrees below average, but off and on rain is in the works as well.  The rain should mostly be light and scattered from sunrise to sunset with accumulations up to a half an inch.  Monday will be mostly dry and sunny, but some energy in our atmosphere may trigger a few light showers over Southern Maryland.  Temperatures should generally be below normal this work week.