Pretty simple. It happens all the time. A warm, moist, low pressure air mass is being forced over a cold, dry, high pressure air mass. The air that holds the moisture is warm enough to produce rain. It produces freezing rain when the high pressure is cold enough, or has been in place long enough to freeze the ground or cars, or whatever. Worst conditions around. You may have to chip through ice to get your car door open. And the roads are the slickest you'll ever see. The irony is that we don't see it very often in the intermountain west. It happens more in places like Texas, Florida, and the Carolinas. Our storm fronts aren't often warm enough. Theirs almost always are. The good news for them is that it usually warms up quickly and melts the ice. We usually get snow on top of the ice and it lasts for a couple of days.
Fishrmn
