Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 416 AM EDT Sun Jul 27 2014 Valid 12Z Sun Jul 27 2014 - 12Z Tue Jul 29 2014 ...Flash flooding and severe weather possible across the Central Appalachians and northern Mid-Atlantic states... ...Another round of cooler and drier Canadian air will spread southeastward through the Central and Eastern U.S.... ...Heavy rains and localized flash flooding expected over southeast Colorado... Showers and thunderstorms will continue to fire up within a moist and unstable airmass in place from the Great Lakes and Ohio Valley into the Northeast and Mid-Atlantic states. A rather robust piece of energy diving down from Canada should help organize some of the thunderstorm activity...especially ahead of a strengthening surface low and cold front crossing the Central Appalachians on Sunday and pushing into the northern Mid-Atlantic states Sunday night. Developing storms could contain heavy downpours...damaging winds...large hail...and even an isolated tornado. Heavy rains and strong storms will continue to be a possibility with this system as it lifts through the Northeast on Monday. Farther south...the cold front will help trigger scattered showers and thunderstorms while dropping through the southern tier of the Nation. A strong surface high setting up over the north central U.S. will bring another round refreshing Canadian air into the Upper Midwest on Sunday. The cooler and drier conditions will spread southeastward through much of the Central and Eastern U.S. early this week. Monsoonal moisture will continue to fuel widespread convection across the Southwest and Central Rockies Sunday and Monday afternoons. Localized areas of flash flooding will be possible across southeast Colorado...where the moisture will interact with a frontal boundary stretched along the front range to produce organized areas of heavy rains. Farther north...temperatures will be on the rise in the Northern Rockies and Northern Intermountain West as an expansive upper ridge sprawled across the south central U.S. builds northward through the region. Gerhardt Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php