Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 225 AM EST Mon Jan 09 2017 Valid 12Z Mon Jan 09 2017 - 12Z Wed Jan 11 2017 ...Periods of heavy rain and snow expected to continue for much of the West through midweek... ...Deepening low pressure expected to bring a mix of rain and snow from the northern plains and Midwest to the Northeast... ...Warming temperatures expected for much of the central and eastern U.S... A series of Pacific storm systems will continue to impact the western U.S. through midweek, bringing periods of rain and snow, some of which could be heavy, to many areas. A cold front will move across the Great Basin and into the Rockies today, lowering snow levels and changing precipitation from rain back to snow by tonight at many lower elevation locations. Snow will also be widespread at the higher elevations of the Rockies and the northern Intermountain region, as well as mountain ranges across the West Coast states. Heavy snow is possible for some of these areas. At the lower elevations along the West Coast, rain will continue for many areas, some of which could be heavy and lead to areas of flooding or flash flooding. Another potent Pacific low pressure system will approach the coast Tuesday afternoon and evening, bringing another round of potentially heavy precipitation. Rising snow levels ahead of this system may once again change some mountain locations over to rain, before changing back to snow as the system moves inland Tuesday night and Wednesday. Upper-level energy will cross the Rockies and move into the plains today, with a low pressure system expected to begin taking shape tonight across the northern plains. Snow is expected to develop today across the northern plains, spreading east into the Midwest and Great Lakes tonight and Tuesday morning. As the low pressure system begins to deepen more quickly across the Midwest on Tuesday, warmer air will be pulled northward, changing snow to rain across much of the Great Lakes by Tuesday afternoon and evening. Farther south, showers and thunderstorms are expected Tuesday and Wednesday from the Ohio valley to the Tennessee and lower Mississippi valleys. Precipitation is also expected to spread into the Northeast on Tuesday, beginning as snow for many areas and then gradually changing to freezing rain or rain Tuesday night and Wednesday morning. An arctic air mass will begin to subside across the eastern U.S., with temperatures warming substantially through midweek across much of the central and eastern U.S. High temperatures today will be 10 to 20 degrees below average across portions of the Southeast and Mid-Atlantic regions. Warmer air will begin building, however, with areas from the southern plains to the Midwest temperatures rising to well above average on Tuesday. Portions of the southern plains and mid-Mississippi valley could see high temperatures 15 to 25 degrees above average on Tuesday. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php