Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 331 AM EDT Mon Jun 29 2015 Valid 12Z Mon Jun 29 2015 - 12Z Wed Jul 01 2015 ...Severe thunderstorms possible for portions of the Midwest and Ohio River valley... ...Well above average temperatures to continue across the Pacific Northwest... A surface low pressure system will move across the Ohio River valley today, resulting in an increase in showers and thunderstorms across this area. The Storm Prediction Center is forecasting a slight risk of severe thunderstorms for portions of the Ohio valley. Please refer to products issued by the SPC for further details on the severe weather threat. Rain and thunderstorms associated with system will spread northeastward into the Lower Great Lakes and portions of the Northeast on Tuesday. A second low pressure system will move from Canada into the Midwest and Upper Great Lakes today. Additional showers and thunderstorms, some of which may be severe, are possible in this area. A strong ridge of high pressure at the mid and upper-levels of the atmosphere will remain in place across the West over the next couple days. Sinking air across the region resulting from the ridge will continue to promote well above average temperatures. High temperatures today and Tuesday will be 10 to 20 degrees above average across much of the northwestern U.S. and northern Intermountain West. Some moisture from the Gulf of Mexico will persist across the West, promoting the development of afternoon showers and thunderstorms, primarily in areas of terrain. Dry conditions will persist across most areas, however. An upper-level disturbance will move along the northern periphery of the ridge tonight into Tuesday. As the disturbance crosses the northern Intermountain states a surface low pressure system will develop and move into the northern plains on Tuesday, bringing a chance of showers and thunderstorms. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php