TENNESSEE, USA — Tonight: Increasing clouds and not as cold with lows in the middle 40s ... Monday: Mostly sunny and warm. Highs in the middle to upper 70s. Lows in the middle 50s Monday ...

Barbed lines indicate the leading edge of travelling cold (and occasionally warm) fronts, the boundaries between different types of air. The term 'front' was applied during World War 1 by European ...