Air Masses of North America

Continental Polar/Arctic -

• Stable, cold, dry air masses originating over N. Canada and Alaska
• eventually plunge southward to interior of U.S. as a shallow dome of high pressure - why???
• can reach Gulf of Mexico and Florida - freeze crops
• Produce lake effect snows as they move over the great lakes.
• Usually do not move west of Rocky mountains - mountains confine cold air to the east. Upslope precipitation is common east of the rockies as the cP air mass slides to the south.
• During the summer, cP air mass can bring relief to hot, humid regions.