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General Characteristics of North American Air Masses in Summer

The exact date for this information is unknown but it may be 1954.

Air Mass Source Region Clouds Ceiling Visibility Turbulence
cP From Canada Scattered afternoon CU Unlimited except in or before showers Good; a few patches of fog Moderate up to 10,000 feet in afternoon
mP From the Pacific over the Pacific coast ST, tops 2000 ft to 5000 ft, frequent at night 100 ft to 2500 ft unlimited during day Poor, especially at night Slightly rough below and in clouds, smooth above
mP From the Pacific east of the mountains Scattered afternoon CU Unlimited Excellent Generally smooth except in lowest layers in afternoon
mP From the Atlantic Broken to overcast SC 800 ft to 2000 ft Good Light below clouds
mT From the Gulf and Atlantic ST or SC in early morning; CU and CB in afternoon Morning 500 ft to 1500 ft; afternoon 2000 ft to 4000 ft Excellent except below clouds in early morning Smooth in early morning, rough in afternoon
cT From Mexico and the Southwest States None Unlimited Excellent Smooth in early morning, rough in afternoon

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last updated on 12/14/10