Ridges and Trough aloft - Highs and Lows at the Surface

500 mb Chart

Notice that ridges aloft are associated with Highs at the surface

Troughs aloft are associated with Lows at the surface.

  Surface Pressure

This association of ridges/troughs with Highs/Lows occurs most of the time, BUT NOT ALWAYS

The surface lows are referred to as (midlatitude) cyclones

The surface highs are referred to as anticyclones