Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 340 AM EDT Tue Aug 13 2013 Valid 12Z Tue Aug 13 2013 - 12Z Thu Aug 15 2013 ...Severe thunderstorms possible over southeast VA into eastern NC... ...Heavy rain and flash flooding possible across the lower Mississippi River valley... ...Noticeable cool-down in the forecast for the northern tier... A frontal boundary moving through the Ohio River valley will continue to push eastward today, spreading showers and thunderstorms along and ahead of it. Another cold front on its heels will merge into the lead boundary and help usher in much cooler and drier air to the Great Lakes and Northeast by tomorrow. Temperatures could bottom out in the 40s outside the immediate I-95 urban corridor and perhaps drop as low as the upper 30s across parts of rural Pennsylvania. To the south, the warm and humid air mass will support a chance of severe weather per the Storm Prediction Center over the southern Mid-Atlantic states into North Carolina as storms fire ahead of the main cold front later today. The heaviest rain may fall over the lower Mississippi River valley through tomorrow due to favorable dynamics and an abundance of moisture. WPC has highlighted a slight risk for flash flooding in this area tomorrow. Farther west along the front, afternoon storms are again likely near and to the east of the Continental Divide with above normal lower-atmospheric moisture combines with afternoon heating. Finally, a system well offshore the Pacific Northwest will gradually edge close enough to Washington/Oregon to increase the chance for some showers along the immediate coast by Wednesday evening. Fracasso Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php