Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 429 PM EDT Thu Oct 30 2014 Valid 00Z Fri Oct 31 2014 - 00Z Sun Nov 02 2014 ...Heavy snow possible for portions of the southern and central Appalachians Friday night and Saturday... ...Well below-average temperatures expected for most of the central and eastern U.S... ...Strong Pacific storm system to bring rain and snow to much of the West and Intermountain West... Both the western and eastern U.S. will see significant weather during the short range forecast period as the upper-level flow across the nation becomes highly amplified. A vigorous upper-level disturbance will dive southward across the Upper Great Lakes tonight and into the Ohio valley on Friday. At the surface, one frontal system will cross the Great Lakes and Ohio Valley while another develops and deepens off the North Carolina coast. A polar high pressure will usher a much colder air mas into the central and eastern U.S. behind the western of the two aforementioned systems, with temperatures 10 to 20 degrees below average in some areas. Rain and snow will be possible across the Great Lakes on Friday as the system crosses the area, with snow for the Ohio valley. The more significant event will begin Friday night into early Saturday, however, as the energy from the two systems begins to combine, and colder air changes rain over to snow across much of the eastern Ohio Valley, and central and southern Appalachians. Upslope flow across the Appalachians with northwesterly flow may enhance snowfall, and heavy snow is possible. Additionally, rain and snow are possible on Saturday across portions of northern interior New England. Another vigorous low-pressure system will move onshore in the West tonight. Widespread precipitation is expected along and in the wake of the surface front. While precipitation will begin as rain at all but the highest elevations of the West, snow levels will gradually lower as the front moves inland and the upper-level trough crosses overhead, so by Saturday snow will become much more commonplace across the Intermountain West. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php