understanding air masses and their impact on the weather

Air mass

Large, distinctive body of air with homogenous characteristics

Source region

Area where air masses originate

Air mass classification

Air masses are named based on their temperature and moisture characteristics

cP and cA air masses

Bitterly cold and dry; form over interior Canada, Arctic basin, and Greenland ice sheet

Lake effect snow

Weather phenomenon resulting from cold air moving over warmer lake waters

mP and mT air masses

Moist air masses that influence North American weather, with mT being dominant in SE summer

Nor'easter

A type of storm that can bring heavy precipitation, especially influential east of the Rockies

Atmospheric river

Narrow bands of circulation transporting large amounts of moisture outside of the tropics

cT

Limited source region; influence limited to summers with unstable air masses

Air mass modification

Process by which air masses change as they migrate away from their source region

Moisture characteristics

Determined by the source region and classified as dry or wet

Temperature characteristics

Determined by the source region and classified as cold or warm

Potentially record setting low temperatures

Can occur when cP air masses spill into the US

mP air masses

May begin as cP over Siberia and reach the west coast of North America with lots of moisture

mT air masses

Less frequent during winter, but when present can lead to precipitation

Summary of air masses

Air masses are large, distinctive bodies of air with homogeneous thermal and moisture characteristics

Source regions for air masses

Include Pacific and Atlantic Oceans, Gulf of Mexico and Caribbean, Southwest US and Mexico, and Interior of Canada and Arctic

Interactions between air masses

Key for weather in the midlatitudes, including phenomena like drought