National Weather Service United States Department of Commerce

Major Storm Arriving Into The Western U.S.

A major Pacific storm system will arrive into the Pacific Northwest and produce locally heavy rain, heavy mountain snow, gusty winds and a slew of marine hazards. This significant storm will dig down the West Coast over the weekend into the Southwestern U.S. For Saturday and Sunday, expect heavy to excessive rainfall along the California coast and widespread heavy mountain snow across the West. Read More >


The December 2015 climate summaries for Big Piney, Buffalo, Casper, Greybull, Lake Yellowstone, Lander, Riverton, Rock Springs, and Worland are now available online.

Overall, December saw near normal temperatures, with mainly below normal precipitation. Sites experiencing slightly below normal precipitation were all but Casper, Lander and Worland. Casper experienced its 6th wettest & 7th snowiest December on record, while Rock Springs and Big Piney had the 3rd & 7th driest Decembers on record. Apart from a warm start to the month with some sites setting a new record high on the 9th, the rest of the month was colder than normal. This was marked by an arctic outbreak in the wake of a storm around Christmas. The area was impacted by 2 major storms, one in the middle of the month, on the 13-16th and Christmas. This snow, coupled with strong winds, closed Interstate 80 for several days due to hazardous road conditions and poor visibility.   See the links below for details for individual sites or click here for Water Year Precipitation summaries for more locations.

If you would like additional/more in-depth climate information, please refer to our Climate Page. Under the Observed Weather tab, you can find the Daily Climate Report (CLI), the Preliminary Monthly Climate Data (CF6), the Monthly Weather Summary (CLM), the Regional and State Summary (RTP/STP). The Daily Climate Report will have the weather data for the day (from midnight to 1159 pm). The Monthly Climate Data will have this data for each day of the month, compilying all the daily data into one form. The Regional and State Summaries will have temperature and precipitation data for various locations across the state, updated 4 times a day.


Big Piney




Lake Yellowstone



Rock Springs


A winter storm brought heavy snow to Casper on 14-16 December. This was the scene on Casper Mountain near Crimson Dawn late in the afternoon on the 15th. Photo courtesy of Ken Brown .