Glossary

High Pressure System

Credit
Environment and Climate Change Canada

A high pressure system over western Canada creates widespread sunshine. Surface winds are generally light, except in this weather map example where tightly packed isobars (lines of equal pressure) near the coastal fjords result in strong outflow winds.

High pressure systems generally result in clearer skies and reduced precipitation. Air within an area of high pressure spirals downward towards the earth’s surface and then spreads outwards in a clockwise manner towards areas of lower pressure, resulting in atmospheric subsidence. 

An area of relatively high atmospheric pressure surrounded on all sides by lower pressure is referred to as a high. An elongated region of high pressure extending from a high is called a ridge.

It is common for surface hoar and facets to form on the snow surface during periods of high pressure, particularly those that last several days. These become a weak layer when they get buried by subsequent storms and can be responsible for persistent slab problems.