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Unique and descriptive terminology has a tendency to be linked with weather and many of its processes. How many times have you heard phrases like "howling winds" or "raining cats and dogs"? These terms give action qualities to some of the wild aspects of weather.

Pineapple Express is another descriptive term that is used frequently in the media and is linked with heavy rain and flooding. Actually, it develops during a relatively common weather pattern with a ridge over the West Coast and a low pressure in the Eastern Pacific. Southwest winds ahead of the low pressure drive warm, moist air over the ridge into the Pacific Northwest and California. This leads to widespread cloud cover, persistEnt rain and unseasonably warm temperatures. The flow of warm air can melt the snow pack in the mountains, while periods of heavy rain occur when the warm moist air is forced over the mountainous terrain. Rapid snow melt paired with heavy rain leads to extensive flooding.

Forecasters often refer to this warm, moist air flow as the Pineapple Express because it originates from the subtropical waters around Hawaii where pineapples are typically grown.

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Spokane Weather Forecast Office
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Spokane, Washington 99224

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