Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 342 PM EDT Fri Oct 18 2013 Valid 00Z Sat Oct 19 2013 - 00Z Mon Oct 21 2013 ...Cool Autumn weather pattern setting up for the Central and Eastern U.S... ...Dry and warm conditions expected for the West Coast... Positive PNA pattern will continue to unfold over the next several days with amplified upper ridge along the West Coast..while a series of shortwave impulses help carve out a broad upper trof over the Great Lakes/Central U.S. This pattern will result in generally dry and warm conditions in the West and especially the West Coast as the main Pacific storm track is forced well north into AK and western Canada. By contrast...evolving northwesterly flow aloft over western Canada will allow for several weak and quick moving systems to tap some of the coolest air of the fall season and drive it southeastward into the lower 48 states. The initial impact of the colder air will be felt across the Northern and Central Plains and Great Lakes through Saturday as a cold front sweeps across the region accompanied by mainly light showers and post frontal lake showers that may be mixed with or change over to snow in some spots. By Sunday...a developing area of low pressure is expected to move eastward from the northern plains bring a mixture of rain and snow to parts of the Upper Mississippi Valley Sunday into Monday. Behind this system..a reinforcing shot of even colder air is expected to invade parts of the Northern/Central Plains and Great Lakes into at least early next week. Across the South...an area of showers and spotty thunderstorms will accompany frontal system that will gradually push south and east across parts of Texas..the Gulf Coast..and the Southeast U.S. Most of the precipitation will be rather disorganized with the exception of parts of the western gulf coast region where deeper moist easterly flow will likely support some concentrated moderate to locally heavy rains Otherwise..most areas in the somewhat cooler air north of the front will be dominated by dry high pressure settling over the Tennessee Valley region during the period. Sullivan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php