Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 417 PM EDT Thu May 16 2013 Valid 00Z Fri May 17 2013 - 00Z Sun May 19 2013 ...Unsettled weather is in store for the northwestern quarter of the Nation... ...Showers and thunderstorms are expected along a frontal boundary stretched from the Mid-Atlantic States to the Central Plains... ...Heavy rains and potentially severe storms will be possible across the Lower/Middle Mississippi and Tennessee Valleys... A long-wave trough amplifying over the western U.S. will keep weather active across the northwestern quarter of the Nation the next few days. Showers and thunderstorms will be possible over the Pacific Northwest and eastward across much of the Intermountain West..Rockies...and Northern Plains. Although precipitation will be fairly widespread...a lack of a significant moisture supply should keep totals on the lighter side. However...some enhanced amounts will be possible over the higher terrain. East of the Rockies...a frontal boundary stretched over the Mid-Atlantic States...Ohio Valley...and westward back into the Central Plains will be the main focus for precipitation heading into the weekend. Scattered showers and thunderstorms will be possible all along the front...and a weak impulse of energy aloft should lead to more organized areas of convection across the Upper Mississippi Valley Thursday night into Friday. Organized areas of convection will also be possible south of the frontal boundary...in the warm sector...where a piece of southern stream energy lifting northeastward through the Middle/Lower Mississippi and Tennessee Valleys will pull plenty of moisture out of the Gulf of Mexico and help ignite showers and thunderstorms. These storms could contain heavy downpours and potentially severe weather. Please refer to the Storm Prediction Center for the latest information on severe weather. Gerhardt Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php