Useful for: combination thickness and mean sea level pressure will show areas experiencing advection of cold air (CAA) with low thickness values or advection of warm air (WAA) with high thickness values. This has effect on the low level temperatures which will increase in WAA and decrease in CAA. Certain thickness values mark air masses eventually separated by fronts: 570 tropical air,  546 = polar front, 510 arctic front.
Useful for: prognoses for wind speed (tight isobars =  rather windy), direction = clock wise around high pressure and anti clock wise around low pressure, and general type of weather (rather poor in a low, and fine in a high).