How Do High Pressure and Low Pressure Affect Our Weather?

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By By Steve Pool

SEATTLE - You're well familiar with our "H" and "L" designations on weather maps for areas of high and low pressure, but what do they mean in regards to what weather's coming?

High pressure situations are generally associated with fair, sunny weather. As high pressure is an area of sinking air, and air tends to dry out as it sinks, leaving sunny skies.

Low pressure areas are generally cloudy/rainy areas -- where strong areas of low pressure bring our stormiest weather. That's because it's an area of rising air, and as air rises, it condenses into clouds and rain. Air moves from higher pressure to lower pressure, so if you have a high and a low nearby, it can be windy as air rushes between the two.

Your Photos

YouNews House destroyed by tree House destroyed by tree
Cottonwood tree felled by today's windstorm destroyed home in Lynnwood. Occupants - fearing the intensity of storm - retreated safely to their basement just minutes before the tree fell. House is a total loss.
YouNews Wild winds turns into 3 totaled cars Wild winds turns into 3 totaled cars
A huge tree, in Lynwood, snapped in half causing branches to brake windshields open, damged equipment, and frontal damge of a car. Started out as simply winds, leading into wilder then moments before causing a rather large tree to fall over and hit three cars.
YouNews Changes on the way Changes on the way
The cloud bands around Mt. Rainier are a sure sign of changing weather conditions. These images of Mt. Rainier were taken Thursday evening around 7:30pm with a Nikon D3000
and a 200mm telephoto lens. The dark spots on the 1st image is flock of birds (not dirt on the lens).