Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 258 AM EST Fri Dec 23 2016 Valid 12Z Fri Dec 23 2016 - 12Z Sun Dec 25 2016 ...Energetic storm system to bring heavy rain and snow to much of the western U.S... ...Fast-moving front to bring rain and snow to much of the central and eastern U.S... ...Above average temperatures expected for much of the central and eastern U.S... Precipitation across the West will become increasingly widespread today as an a low pressure pressure pushes inland. Rain is expected across much of California, with snow in the Sierras - the coastal areas may have periods of heavy rainfall, as well as, the higher elevations of California, the Pacific Northwest and the Intermountain West may have heavy snow. The extent of the heavy snow will spread across much of the Rockies and the adjacent northern Plains on Saturday as the system moves east. Snow levels will lower as the upper-level trough moves inland, and snow is expected to eventually fall at all but the lowest valley elevations. A vast majority of the counties from central Washington/Oregon to Minnesota/Wisconsin have winter weather advisories, winter storm watches and blizzard watches in effect. Holiday travel will likely be adversely impacted by this system - travelers are strongly encouraged to stay tuned to weather updates, allow extra time to arrive safely or consider alternative routes. Light snow and freezing rain will be possible across portions of the central U.S. today as a fast-moving surface front passes through. Warm, moist air will stream northward from the Gulf and will aid in increasing rain amounts from the lower Mississippi Valley to the Tennessee and Ohio Valleys. A few thunderstorms will be possible across the lower Mississippi valley, where more unstable air will be in place. Cold air sinking into the Great Lakes area will reinforce the snow generation from the Upper Midwest to portions of the Northeast. Mild temperatures are forecast for much of the central and eastern states though Saturday. Some locations are expected to have maximum temperatures to be 5 to 15 degrees above average. However, forecast highs will steadily fall across the West as cold air filters in behind the frontal passage. Many locations will 5 to 15 degrees below average along the West Coast, as well as across the Great Basin, Intermountain West, and portions of the Southwest. Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php