Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 317 AM EDT Thu Jul 11 2013 Valid 12Z Thu Jul 11 2013 - 12Z Sat Jul 13 2013 ...Cooler and drier air continues to move from the Upper Mississippi Valley across the Great Lakes, Ohio Valley into western sections of the Northeast... ...A cold front along the leading edge of the cooler air may stall along the East Coast, possibly bringing locally heavy rains to Middle Atlantic states to southern New England... ...Midsummer heat is expected to continue across the Southwest and South Central States and reach northward across the Northern Rockies before cooler air approaches from the West... High pressure from Canada will continue to bring relatively cool and dry conditions from the Northern Plains across the upper Mississippi Valley, Midwest and Ohio Valley before pushing south and eastward across portions of the Tennessee Valley and much of the Northeast. This airmass should be a welcome relief from the high temperatures, high dewpoints and thunderstorms that are more typical this time of year. A cold front continues to move south and eastward from the Mid Mississippi to Ohio Valleys associated with scattered showers and storms. While most showers and thunderstorms have diminished overnight, there are still a few pockets of storms especially over the Southeast that continue to bring heavy rain. As the front approaches the East Coast on Thursday, it is expected to slow down as an upper low cuts off from the main jet stream. This upper low could remain along the East Coast into Saturday. The combination of the slow movement of the system in concert with a stationary surface front could result in another period of heavy rainfall for portions of the East Coast. Showers and thunderstorms could be quite heavy near or along the front. Farther west, hot temperatures will remain over the Southwest and build north and eastward into the central and northern Rockies where temperatures in the 90s to near 100 degrees will occur as far north as Wyoming and Montana. Cooler air working its way eastward from the Pacific Northwest will bring an end to the heat in Montana by Friday but the heat will then spread into the Northern and Central Plains under an expanding upper ridge. Monsoonal moisture circulating around the western periphery of the upper ridge will continue to bring moisture from the eastern Pacific northward across the Southwest, the Great Basin and the Rockies, resulting in mostly afternoon and evening thunderstorms. Moisture may even make its way again across southern California with showers and storms across the Interior as well as a few showers possible even along the coast, a rarity in July. In some desert locations of the Southwest, particularly in southern Nevada, Arizona and New Mexico, thunderstorms raise the risk of possible flash flooding and severe weather. Kocin Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php