Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 239 AM EST Tue Jan 10 2017 Valid 12Z Tue Jan 10 2017 - 12Z Thu Jan 12 2017 ...Periods of heavy rain and snow expected to continue for much of the West through midweek... ...Low pressure system expected to bring rain and snow from the 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. Onshore flow will continue to spread moisture into the West today ahead of another Pacific low pressure system, which will approach the coast this afternoon. Widespread precipitation is expected, with heavy rain and even a few thunderstorms possible for much of California. Snow levels will rise as the system approaches, with snow changing to rain or a mix of rain and snow across portions of the Sierras and the Great Basin. Meanwhile snow, potentially heavy for some areas, will persist from the interior Pacific Northwest to the northern and central Rockies. Rain and snow will begin to become more scattered by late Wednesday as the system moves inland and weakens. Another somewhat weaker low pressure system will bring more rain and mountain snow to the West Coast states on Wednesday, although precipitation will not be as widespread or as heavy as with previous storm systems. Snow will fall across areas from the Upper Midwest to the Great Lakes this morning as a developing low pressure system crosses the region. The surface low will begin to deepen quickly across the Upper Great Lakes later today. As the low deepens, warmer air will be transported northward, changing snow to rain across much of the Great Lakes by this afternoon and evening. Farther south, showers and thunderstorms are expected today and Wednesday from the Ohio valley to the Tennessee and lower Mississippi valleys. Precipitation is also expected to spread into the Northeast today, beginning as snow for many areas and then gradually changing to freezing rain or rain tonight into Wednesday morning. A second cold front will quickly move into the Midwest later Wednesday, bringing another round of rain to much of the Ohio valley and southern Great Lakes, with snow and areas of freezing rain for the Upper Midwest. Temperatures will warm substantially through midweek across much of the central and eastern U.S. High temperatures today are forecast to be 15 to 25 degrees above average from the southern plains and lower Mississippi valley to the Great Lakes. Temperatures will remain slightly below average along much of the East Coast today, but these areas will warm up quickly by Wednesday, with high temperatures expected to be 5 to 10 degrees above average. Even warmer temperatures are expected for much of the eastern U.S. by Thursday. Meanwhile, another round of arctic air will spread into the northern Rockies and northern plains today and Wednesday, with high temperatures expected to be 15 to 25 degrees below average. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php