The deluge of snow in the mountains is coming from a weather pattern called the Pineapple Express.
Large scale winds flow over our oceans. They're called Trade Winds. Typically in the tropics these winds push water from the east to the west.
The related (but opposite) flow further North, sometimes called the "anti" trades, push water toward the U.S. coastline.
This explains the way our weather moves, but isn't enough to produce intense precipitation. Sometimes narrow bands of stronger winds form and carry concentrated moisture with them. This is called an Atmospheric River, because it's similar to a river of water on land.
A special type of atmospheric river is called a Pineapple Express. They form when low pressure is west of California with high pressure to the south near Mexico.
That's what happened this week. In this set up, these two systems squeeze air forming a strong corridor wind that pulls very warm water from Hawaii toward California… which is where the name Pineapple Express comes from. These events tend to be strong and carry vast amounts of water.
While the main region that benefits from this moisture are the coastal states… some of this moisture often pushes further inland and can hit the Rockies as it is doing this week.
For the most part, this moisture is staying west of Southern Colorado. But not completely. A chunk of the moisture will wrap around and impact us here at home this weekend.
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