File:Western United States (MODIS 2018-05-01).jpg

English: The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra satellite acquired a true-color image of the snow-capped mountains of the western United States on April 26, 2018. For orientation, the Great Salt Lake, Utah, appears green and is located just south and west of center of the image. The snow-topped mountains are parts of the Rocky Mountains which sit in the following states, from southeast to northwest: Colorado, Wyoming, and Idaho.

The snow that accumulates in the western mountains is vital to the welfare of the region. Much of the annual precipitation occurs as winter snow and is stored as “snow pack” until the springtime, when warming temperatures cause the snow to begin to melt. The spring melt fills reservoirs, greens dry grasslands and pasturelands, and aids in agriculture.

According to the National Integrated Drought Information System (NIDS), while April storms brought additional snow to the mountains, much of the region continues to suffer from “snow drought”. Snow drought is defined as a period of abnormally low snowpack for the time of year. It is caused by either below-normal cold-season precipitation (dry snow drought) or a lack of snow accumulation despite near-normal precipitation (warm snow drought) which is caused by warm temperatures and precipitation falling as rain rather than snow or unusually early snowmelt.

As of April 26, NIDS reported snowpack is well below normal in the southern two thirds of Oregon, southwest Idaho, through the Great Basin and including the four corners region. Snowpack in the Gunnison Basin of Colorado is also well below average. One area above normal is the north Cascades, in the Skagit Basin of Washington, where wet April weather continues to provide additional snow.