Kristen's Classroom: Pineapple Express? It's a real thing!

AUSTIN (KXAN) -- While Texas enjoys the sunshine and warmth this week, parts of California are getting pummeled by heavy rain and mountain snow brought on by an atmospheric river.

But what is an atmospheric river? And why do people call it the Pineapple Express?

Atmospheric river

Defined by the National Oceanic and Atmospheric Administration, atmospheric rivers are "relatively long, narrow regions in the atmosphere – like rivers in the sky – that transport most of the water vapor outside of the tropics". They often bring beneficial rain to parts of the West Coast, but can sometimes result in too much of a good thing causing flooding, debris flows, and mudslides.

Atmospheric rivers are rated on a 5-category scale that considers strength, impact and duration. For example, a Category 1 atmospheric event is considered "primarily beneficial"... while a Category 5 is deemed "primarily hazardous".

The Pineapple Express

Atmospheric rivers are common in the West, with the most prominent being the Pineapple Express. This band of atmospheric moisture originates in the tropical Pacific around Hawaii and can transport a tremendous amount of water to the U.S. and Canada's West Coasts.