Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 159 PM EDT Wed Jul 05 2017 Valid 00Z Thu Jul 06 2017 - 00Z Sat Jul 08 2017 ...Heavy rain possible from portions of the mid-Mississippi valley to the Mid-Atlantic... ...Severe thunderstorms possible through Thursday for portions of the Midwest and Upper Great Lakes... ...Temperatures are expected to be well above average from the Northwest to the northern Rockies... A slow-moving upper-level disturbance and multiple waves of low pressure along a surface frontal boundary will bring scattered to numerous showers and thunderstorms from the mid-Mississippi valley to the Mid-Atlantic region tonight through Thursday. A highly moist air mass in place will be sufficient to produce heavy rainfall for some areas, and isolated flash flooding is possible. On Friday, the system is forecast to consolidate into a single area of low pressure along the New England coastline, as it continues to bring numerous of showers and storms from the central Appalachians to the Northeast, with scattered storms elsewhere across the eastern U.S. A secondary frontal boundary farther north is also expected to bring scattered showers and thunderstorms to the Midwest and Upper Great Lakes tonight and Thursday, some of which could be severe. Please refer to products issued by the Storm Prediction Center for further details on the severe weather threat. Across the western U.S., a large upper-level ridge of high pressure will dominate the weather pattern through the end of the work week. Sufficient moisture and instability will be in place beneath the ridge for isolated to scattered thunderstorms across much of the interior west, particularly during the afternoon and evening. The ridge will support well above average temperatures, particularly from the Northwest to the northern Rockies, where afternoon highs on Thursday and Friday are forecast to be 10 to 20 degrees above average. Temperatures across the interior Northwest and northern Great Basin may surpass 100 degrees in some areas. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php