The term overrunning precipitation refers to excess moisture that develops far out in front a low pressure. This “tongue” of precipitation usually extends out 400+ miles in front of the low pressure. Many times this area where high and low pressure come together ahead of the actually front is referred to as the “zone or area of truncation”. Truncation is a place where two things merge and within the fluid atmosphere there area naturally these points. When this merger occurs, the two meet and lift occurs. The cold moves in over the top and the warm air rises. When this occurs far out in front of the actual low pressure, interesting weather can unfold for WNC. A particular event comes to mind when review overrunning events and some of you can recall the somewhat(AshevilleWX called for 6 “-10”) surprise snow of December 2017. This overrunning event caught some off guard and some forecasts were only for a dusting. A low pressure had developed on The US/Mexico border and a strong high pressure was in place to our Northeast. An area of truncation developed over WNC, and snow was the result because the low pressure/warm nose was so far away.