an Isobaric line is a line of constant pressure. In meteorology, this would be to mark regions of the same atmospheric pressure. Storm fronts occur along regions where high low pressure meet. By looking at a map of isobars you could tell where a storm front is by looking at the differences between pairs of adjacent isobars (gradient). If isobars are closer together then there is a larger pressure differential, and therefore would suggest a high-low pressure region where a front could exist.
