Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 352 AM EDT Sat Jun 27 2015 Valid 12Z Sat Jun 27 2015 - 12Z Mon Jun 29 2015 ...Severe thunderstorms and flash flooding possible from eastern portions of the Ohio valley to the Mid-Atlantic/Southeast... ...Well above average temperatures expected for much of the western U.S... A vigorous low pressure system moving across the Ohio River valley this morning will move northeastward toward the Lower Great Lakes today, with the associated cold front moving eastward across the central/southern Appalachians and into the Mid-Atlantic states by this evening. Widespread showers and thunderstorms are expected to accompany this system. A steady, soaking rain is expected north of the surface low across the Lower Great Lakes eastward into the Northeast by this evening. Farther south, warm, moist and unstable air being pulled northward into the system will result in showers and thunderstorms. Showers and thunderstorms are forecast to be particularly widespread from the central and southern Appalachians eastward into the Mid-Atlantic states this afternoon and evening. Some thunderstorms across these ares may be severe. Please refer to products issued by the Storm Prediction Center for further details on the severe weather threat. Heavy rain may also result in flash flooding as some areas may experience multiple rounds of showers and thunderstorms. Rain and thunderstorms will continue to spread across the Northeast Saturday night into Sunday morning; while the Mid-Atlantic will begin to clear out. Farther south, across portions of the Southeast and Gulf Coast, generally scattered showers and thunderstorms will continue throughout the weekend as the tail end of the frontal boundary becomes stationary. Across the West, high pressure at the mid and upper-levels of the atmosphere will continue to dominate the weather pattern. Sinking air promoted by the ridge of high pressure will continue to result in well above average temperatures. Afternoon high temperatures across the Northwest are forecast to be 15 to nearly 30 degrees above average in some areas, with much of the interior Northwest reaching 100 degrees or higher. Return flow from the Gulf of Mexico will transport some moisture into the West, resulting in a few scattered thunderstorms primarily across portions of the Southwest. Isolated to scattered thunderstorms are also possible in some of the higher terrain areas of the Intermountain West. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php