This map displays the observed pressure at a given station adjusted to sea level for that station’s elevation using an algorithm. This algorithm corrects observed pressures at altitude to MSLP using standard atmosphere data that defines what the average pressure is at any given altitude. The observed deviation from the station’s altitude average is then used to calculate the deviation from the sea level average (1013mb) and thus what the pressure would be at that station if it was at sea level. Use this map to find areas of high pressure (generally calm weather) and areas of low pressure (generally inclement weather).