Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 359 PM EDT Thu Apr 13 2017 Valid 00Z Fri Apr 14 2017 - 00Z Sun Apr 16 2017 ...Cool and unsettled weather over the northwestern U.S. should begin to improve by Saturday... ...Heavy rain and thunderstorms are expected to spread northeastward across the central Plains into the Great Lakes during the next couple of days... ...Above normal temperatures will prevail from the central Plains eastward into the Appalachians... The weather pattern during the next couple of days will be dominated by a retreating upper-level trough in the western U.S. while general ridging is indicated over the eastern two-thirds of the country. The upper-level trough that is responsible for the cool and wet conditions over the Pacific Northwest coast will begin to retreat into Canada during the next couple of days. This will bring mountain snow across the Great Basin and Intermountain West, including the Sierra Nevada through tonight behind a sharp cold front. The precipitation will then head farther northeastward toward the northern Rockies on Friday before gradually tapering off on Saturday. On the other side of the cold front, temperatures will be above normal from the central Plains eastward under the upper-level ridge and a long fetch of south to southeasterly flow at the surface. Meanwhile, an organized area of thunderstorms in the southern High Plains should spread northeastward across the central Plains, reaching the Great Lakes by Saturday ahead of the cold front, which is forecast to edge into the central Plains. Much of the eastern U.S. will remain under the influence of ridging aloft as a strong surface high pressure system moves off New England by Saturday. This will provide generally fine conditions with above normal temperatures over the interior sections during the next couple of days. East of the Appalachians, a persistent east to northeasterly flow from the high pressure center in New England will keep temperatures near or slightly cooler than normal along the East Coast. Kong Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php