Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 257 AM EST Mon Dec 18 2017 Valid 12Z Mon Dec 18 2017 - 12Z Wed Dec 20 2017 ...Heavy snows likely across the Cascades and the northern Rockies on Tuesday... ...Heavy rainfall and flash flooding possible across portions of the Lower Mississippi Valley into the Tennessee Valley on Tuesday... The work week across the Pacific Northwest starts out with some general rain and mountain snows across the higher peaks of the Washington Cascades and the Northern Rockies on Monday. By Tuesday however, a cold front moving inland will bring increased moisture to much of the Northwest. Expect heavy rainfall along the Washington, Oregon, and northern California coasts, with heavy snowfall in the mountains. For much of the Cascades range and the Northern Rockies, upwards of a foot, maybe 2 feet, of snow is possible. Moisture streaming northward from the Gulf of Mexico will keep showers and thunderstorms in the forecast across the Southern Plains and the Gulf Coast states the next couple of days. Heavy rainfall is expected to develop across portions of the Lower Mississippi Valley and into the Tennessee Valley on Tuesday as a warm front lifts northward into the region and a surface low develops across Texas. The heaviest rainfall should focus along the boundary from the ArkLaTex region into the Tennessee Valley where as much as 3 to 4 inches of rain may be possible on Tuesday and into early Wednesday. WPC is highlighting a slight risk for flash flooding across this region as well. Elsewhere, expect mainly light rain or snow showers across the Northeast today as a warm front lifts through. Farther west, a cold front moving across the Upper Great Lakes will keep snow in the forecast on Monday, with more rain spreading into the Northeast on Tuesday, eventually changing over to snow as colder air filters in behind the cold front. Santorelli Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php