NOAA's National Centers for Environmental Information
The two satellite-derived animations above show the daily snow cover across the Northern Hemisphere (left map) and North America (right map) throughout April 2006. By clicking on the images, the change in sea-ice extent across parts of the Arctic can be seen through the month as well as several significant snowfall events across the U.S. and Europe, including a significant US northern Plains storm on the 18th-19th that dumped over 50 inches of snow locally in South Dakota.The seasonal retreat of snow cover can be seen in both animations as a record warm April in the U.S. and above average seasonal warmth across the Northern Hemisphere augmented the average seasonal snow cover extent decrease.
More information on significant winter weather and other hazards can be found on NCDC's Hazards page.
The map to the left depicts percent of average snowpack in the West and Alaska as of May 1st. The snowpack is less than 50% of average across much of the Southwest region causing rising concern over spring water supply, which primarily results from melting snow. Abundant snowfall accumulated in parts of the Northwest through the winter and early spring, with abundant snowfall in the Sierra Nevada in early April. More information on April weather can also be found on NCDC's Hazards page, while information on the southwestern drought can be found on NCDC's monthly drought pages.