You are driving west in your car on a clear, warm day. up ahead, you see a dark band of ominous clouds. soon, you drive beneath the towering bank of clouds, and things get very dark. for twenty minutes, you are pelted with rain and even some hail. you keep driving west, even though it seems a little sketchy at times. on the radio, you hear that the next county to the north is under a tornado warning. then the sky lightens, and there is only a little rain. you notice that the temperature outside has dropped by 15°f (8°c). what have you just driven across?

You have just driven across the Cold front.

Explanation:

Weather Front:

In Meteorology, weather fronts are simply boundaries between two air masses of different densities. There are four weather fronts and one of them is cold front and other fronts are warm front, stationary front and occluded front.

Cold Front:

In Meteorology, cold front is a boundary of cold air mass that is advancing under the warm air mass.

In our scenario, as the driver was moving in the west and he listened on radio, the next country on north is under tornado warning. So, when he passed the cold front, he experienced the conditions described.

i think it is non rem sleep

compass can be used day and night, cloudy or sunny