The mountains all around the Grand Valley are beautiful and provide us with many uses such as hiking, biking, skiing and much more. But did you know that they also greatly affect our weather? The layout of the Grand Valley is at a 90 degree angle running from southeast then turning to the southwest. As storms approach the Grand Valley the surrounding mountain ranges block their direct approach and cause the storms to adapt. This can cause some noticeable differences. We don't see a ton of snow here in the Grand Valley, but have you ever noticed that when it does snow the amounts can vary within just a few miles?
As a storm approaches from the southwest it runs into the Umcompahgre Plateau. As the storm is forced over the higher elevation it pushes the lower levels of the storm up into the upper levels compressing the storm. A storm is like this sponge reaching up tens of thousands of feet and only able to hold so much moisture. As it moves up the slope the lower levels are forced up into the upper levels compressing the storm. This compression forces moisture out of the storm. The result is harder snowfall on the windward or approaching side of the mountain range as the storm travels up the steep slope.
As the storm flows over the range and down into the valley the compression is released and the storm expands back to its original size.
This expansion on the leeward side or valley side of the range allows the storm to be able to hold more moisture which in turn causes it to stop snowing.
But the curvature of the Grand Valley around the plateau allows part of the storm to have a doorway to pass straight through. Storms with a strong southwest flow favor the west end of the valley. Without the lift to this portion of the storm, it is unaffected and continues to snow at the same rate. This is why we can see greater snowfall amounts as we travel to the west end of the valley to places like Fruita, in some cases we can see four to six inch differences just five miles up the road.
The opposite happens if we have a storm approaching from the northwest. As a storm is funneled through the valley it runs into another kind of road block the Grand Mesa. This narrowing of the valley floor causes the storm to compress from the sides and forces the moisture out as it moves through the narrowing passage way.
In this case we will see little snowfall amounts in the northwest end which is Fruita and increasing amounts as we head through Grand Junction towards the southeast.