Minature Upslope Storm

My husband and I took a quick trip to the San Luis Valley of southern Colorado last week to see the largest migration left in North America — The Sandhill Cranes! Up to 20,000 Cranes and 20,000 other ducks, geese, coots, plovers and any other type of waterbird that you can imagine migrate through the San Luis Valley from February to April. They stop to fuel up in the rich salt marshes for their trek to Canada, Alaska and even Siberia. When they move on depends on the weather.

Unfortunately, by the time we got there, the Cranes had left the Valley.

But the San Luis Valley is such an interesting place that we found plenty of other things to keep us interested. One of the most interesting that we saw was purely by chance — a cloud getting caught on the top of Blanca Peak.

 

Image

Warm moist air runs into 14,345 foot Blanca Peak. See how the cloud gets higher as it gets closer to the Peak? It is probably snowing at the summit. Then, once it’s over the top, POOOF! The cloud is gone.

 

This is actually a small upslope storm created as warm moist air coming up from the south (right) is forced to rise to get over the mountain. As the air rises, it cools. As it cools, it forms a cloud. Once the moist air is over the top, it can expand again and it evaporates. Climate people call this orthographic lift.

March through May is the season of upslope storms in Colorado, as warmer temperatures begin to pump air up from the Gulf of Mexico onto the Great Plains and from the Pacific into the Four Corners and San Juan Mountains. The process is exactly the same as what you see here, in miniature. These spring storms bring Colorado most of our moisture, and account for most of our snowpack.

Image