Let us start arbitrarily by beginning the drawing of the 1020-mb isobar in nebraska. north platte, ne would be on a 1020-isobar line generally running north-south. three other isobar lines are noted or needed through the eastern part of the state, given the 4-millibar interval convention. these three lines will separate values where the lower value on the map remains to one side while higher values are on the other side. the pressure values of locations generally east of north platte are therefore 1020 mb.