Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 425 PM EDT Sun Jun 25 2017 Valid 00Z Mon Jun 26 2017 - 00Z Wed Jun 28 2017 ...Thunderstorms could be strong to severe from the southern Rockies into the southern High Plains through tonight... ...The heat over the Pacific Northwest will abate by tomorrow... ...Much of the eastern two-thirds of the country will remain cooler than normal for the next couple of days... A broad trough aloft will continue to be the dominant feature over the eastern two-thirds of the country for the next couple of days. At the lower levels, a high pressure system, reminiscent of a cold season arctic outbreak, is forecast to build southeastward across the Plains and eastward into the East Coast during the next couple of days. This will keep temperatures much cooler than normal with mostly clear skies from the Plains eastward to the East Coast, making for very pleasant conditions for late June. Over the Great Lakes into New England however, disturbances associated with reinforcing shots of cool air from Canada will keep a good chance of showers and thunderstorms around through Monday before tapering off gradually from west to east on Tuesday as the broad upper trough weakens. The disturbances will also help the formation of secondary cold fronts along the East Coast, which is pretty unusual for late June. Along the southern flank of the cool air mass, a stationary front will linger from along the southeast U.S. coast down to the Gulf Coast. The front will provide a focus for scattered showers and thunderstorms, especially during the afternoon and evening. Near the tail end of the front, thunderstorms could become severe tonight from the southern Rockies of New Mexico into the adjacent High Plains under an upper-level disturbance. Farther north, scattered showers and storms are expected to form ahead of a secondary front over the central Plains on Monday. The front, or a weakness in the high pressure system, will push to the south and east, bringing the storms farther down into the mid-Mississippi Valley by Monday evening before spreading eastward into the East Coast on Tuesday. Out West, heat has been the story for the past couple of days over the Pacific Northwest. A cold front from the eastern Pacific is forecast to arrive tomorrow, bringing showers and thunderstorms across the interior mountains into the northern Rockies, reaching the northern High Plains by Tuesday. This will usher in the much cooler marine air back into the Pacific Northwest, ending the recent heat wave. Meanwhile, the northern and central Plains will begin to see showers and thunderstorms forming near and ahead of a warm front as a low pressure system is forecast to develop in the northern High Plains. Over the Desert Southwest, the heat will gradually abate day by day. However, the recent extreme heat and dry conditions will continue to increase fire danger in the area. Kong Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php