Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 143 PM EST Fri Dec 02 2016 Valid 00Z Sat Dec 03 2016 - 00Z Mon Dec 05 2016 ...Heavy rain possible across portions of the western Gulf Coast States and lower Mississippi valley... ...Well below average temperatures expected this weekend across portions of the southern plains... ...Periods of rain and mountain snow expected for the Northwest through the weekend... A vigorous upper-level trough over the southwestern U.S. this afternoon is forecast to deepen into an anomalous closed upper-level low over northern Mexico by early Saturday morning. East of the upper low, a warm front will move slowly north toward the western Gulf Coast. Deep southerly flow east of the upper low will cross this frontal boundary and is expected to result in widespread rain and thunderstorms from the southern plains to the western Gulf Coast and lower Mississippi valley tonight and Saturday. On Sunday, as the upper low begins to move east, and an area of low pressure develops along the frontal boundary, widespread rain and thunderstorms are expected to move east into the southeastern U.S. Heavy rain will be possible across portions of the western Gulf Coast and lower Mississippi valley on Saturday and Sunday. Cold air will be in place on the north side of the low pressure system, across the southern High Plains. Afternoon high temperatures across this area are forecast to be 10 to 20 degrees below average this weekend. In this cold air, a wintry mix of snow, sleet, and freezing rain is possible tonight and Saturday morning from portions of New Mexico east into portions of the southern High Plains. As the system moves east, a generally light mix of rain and snow is possible Saturday night and Sunday from the Ohio valley and Great Lakes to portions of the Mid-Atlantic. The Northwest will remain unsettled through the weekend, with a series of Pacific frontal systems impacting the region. These systems will bring rain to coastal areas and inland valleys, and snow to higher elevations. The most widespread precipitation across the Northwest will occur Saturday night into Sunday as a stronger front moves onshore. As this front moves inland, snow levels will lower as colder air moves into the region. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php