Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 222 PM EST Sat Dec 31 2016 Valid 00Z Sun Jan 01 2017 - 00Z Tue Jan 03 2017 ...Flash flooding possible across portions of the Gulf Coast... ...Heavy rain and severe thunderstorms possible across portions of the southern U.S... ...Heavy snow possible from portions of the Pacific Northwest to the northern Rockies... A low pressure system will move eastward from Ontario into Quebec tonight, with the surface low center moving just north of the U.S./Canada border. The system will bring areas of snow to the Northeast through tonight. Snowfall accumulations are forecast to generally be light, although amounts heavy enough to cause some minor travel disruptions are possible, especially at higher elevations, and across portions of eastern Maine, where winter weather advisories are in effect. Farther south, the trailing cold front associated with this system will become stationary across the Ohio and lower Mississippi valleys tonight. An additional frontal boundary will drift slowly northward across the Gulf Coast states. The result will be numerous showers and thunderstorms through Sunday from portions of the southern plains to the Southeast. Rain may be heavy across portions of the Gulf Coast, from southern Louisiana to the western Florida Panhandle, and flash flooding is possible. Additionally, severe thunderstorms are possible on Sunday across portions of the southern plains and western Gulf Coast. By Monday, the arrival of a rather strong upper-level disturbance will result in an expansion of shower and thunderstorms activity north into the Tennessee and Ohio valleys. Heavy rain will once again be possible across portions of the Gulf Coast and Southeast. Farther west, an upper-level trough will dig into the Pacific Northwest tonight and will persist through Monday. At the surface, a cold front will move southward across the Pacific Northwest through the next couple days, ushering a cold, arctic air mass into the region. Coastal rain and inland snow are expected tonight as a gradually weakening Pacific frontal system moves inland. As the upper-level trough persists overhead on Sunday, areas of snow are expected across a large portion of the western U.S., from the Northwest to the Rockies. As the arctic cold front presses south into the region, snow levels will lower, and rain is expected to mix with and eventually change to snow Sunday and Sunday night even across coastal areas of Oregon and northern California. Heavy snow is possible for some areas. On Monday, the upper-level trough will break into two pieces of energy, with one forming a cutoff low off the Pacific Northwest coast, and the other upper-level disturbance moving east into the northern plains. This will keep snow in place across portions of the Northwest, with snow also spreading east into the northern plains and Upper Midwest in association with that disturbance. Areas of freezing rain are also possible by Monday from portions of the central/northern plains to the Midwest. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php