Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 146 AM EDT Thu Aug 4 2016 Valid 12Z Thu Aug 4 2016 - 12Z Sat Aug 6 2016 ...Cooler air will move across much of the northern U.S. while summer heat continues for the rest of the country... ...Heavy rain and flash flooding possible for the southern Rockies... A potent upper level disturbance tracking eastward along the U.S./Canadian border at the start of the forecast period will sustain a well-defined surface low that is forecast to track northeastward towards Hudson Bay. Severe thunderstorms are likely to develop ahead of the trailing cold front across the Upper Midwest through Thursday night, followed by a cooler and drier air mass from the northwest. By the end of the week, another upper level low will approach the Pacific Northwest and this will increase the coverage of showers and thunderstorms, along with cooler temperatures The area of the country with the greatest potential for heavy rain and flash flooding will be the 4-corners region, especially the higher terrain of Arizona, Colorado, and New Mexico. An enhanced monsoonal flow over this region south of a frontal boundary will result in the development of numerous showers and thunderstorms each afternoon and evening, and some areas may receive in excess of 2 inches of rainfall over a 2 day period. Flash flood watches are in effect for an expansive area from eastern California to northern New Mexico. The heat and humidity are forecast to continue unabated across much of the central and southern U.S. Dewpoints well into the 70s along with daytime highs in the 90s to near 100 degrees will be commonplace from the central Plains to the Deep South. Heat advisories are in effect from eastern Kansas to Alabama where heat indices could easily be in the 100 to 110 degree range, perhaps even higher at times. Hamrick Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php