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MARITIME POLAR AIR MASS

METEOROLOGIST JEFF HABY

The source region for mP air is over cold ocean currents or high latitude ocean waters. This air does not have as much moisture content as mT air. Since mP air is always near saturation, orographic lifting of the air mass can produce widespread rain or snow. This air mass is notorious for producing fog, drizzle, cloudy weather and long lasting light to moderate rain. The temperature of mP air ranges from just above freezing to below 70 degrees F. mP air is modified as it moves over elevated terrain. On the windward side of mountain ranges, mP air can produce an abundance of rain and snow. Once on the lee side of mountains, the mP airmass modifies into a continental airmass. These air masses produce cold fronts but the air is not as cold as polar or arctic fronts. They are often termed "Pacific fronts" or "back-door cold fronts". Maritime Polar air occurs frequently in the Pacific Northwest and to a lesser degree in New England.