A polar vortex dipping down from Siberia is bringing a cold front with frigid temperatures to millions Americans. See maps of the arctic blast.

which helps to predict weather patterns. High pressure often represents stable air, while low pressure can signify instability. On a cold, sunny day there will be a significantly higher ...

The advisories impact large areas of Idaho, Oregon, Montana and Washington, lasting through the end of January.

because those giant H’s and L’s representing high and low air pressure systems on a weather map are meaningless without understanding their significance. HELP FROM HIGH PRESSURE: How Houston's ...