Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 418 PM EDT Sat Oct 19 2013 Valid 00Z Sun Oct 20 2013 - 00Z Tue Oct 22 2013 ...Seasonably cool conditions expected from the Great Plains to the Atlantic Coast... ...Snow will be possible across portions of the Upper Midwest and Upper Great Lakes... A broad upper trough carving out over the eastern half of the country will keep conditions seasonably cool from the Great Plains to the Atlantic Coast during the short range period. Despite a limited moisture supply...a piece of energy aloft lifting around the base of the trough should help trigger light to moderate precipitation across the northern Mid-Atlantic and New England states Saturday night into Sunday. A second...more vigorous...piece of energy rounding the upper trough will drop a surface wave through the northern tier Saturday night and then intensify the low while it slides towards the Upper Great Lakes on Sunday. Again...a lack of moisture will keep precipitation totals light to moderate with this system...but broad cyclonic flow over warm waters should help enhance totals downwind of the Great Lakes. Also...this system will bring a reinforcing shot of cooler air and chance for snow across portions of the Upper Midwest and Upper Great Lakes. A cold front pushing off the Eastern Seaboard Saturday night will stall and linger over the Southeast and across the Gulf of Mexico...serving as a focal point for convection the next few days. Much of the activity will be scattered in nature...but as the tail end of the boundary surges northward during the later half of the forecast period...some heavier and more organized areas of storms could reach the Western Gulf Coast. Out West...an expansive upper ridge centered off the Pacific Coast will keep the Western U.S. relatively warm and precipitation free for the remainder of the weekend and into early next week. Gerhardt Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php