Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 424 PM EDT Tue Aug 06 2024 Valid 00Z Wed Aug 07 2024 - 00Z Fri Aug 09 2024 ...Potentially catastrophic flooding associated with Tropical Storm Debby to impact portions of South and North Carolina... ...Increased flash flood potential for portions of the Desert Southwest and northern Mid-Atlantic this evening and Wednesday... ...Excessive heat for the Southern Plains to the central Gulf Coast through Thursday while the Northern Plains... Tropical Storm Debby is expected to track very slowly northward from its Tuesday afternoon position near the southern South Carolina coast through Thursday night, after briefly moving back out over the western Atlantic ocean tonight. The slow movement will continue to support areas of heavy rain which are going to fall over the central and eastern Carolinas over the next 48 hours. Additional rainfall totals of 10-20 inches, with maximum amounts of 25 inches, are expected which will likely result in areas of catastrophic flooding. Urban and areal flooding along with major flooding of area rivers and streams are expected due to the excessive runoff of heavy rain. In addition, Debby will bring a threat for tornadoes to coastal sections of the Carolinas through tomorrow, spreading northward into southeastern Virginia for Thursday. For additional information on Debby, please visit hurricanes.gov. Farther north into the norther Mid-Atlantic region, deep moisture related to Debby along with a slow moving cold front and favorable wind shear aloft will support the generation of thunderstorms through tonight from portions of eastern Ohio into the New York City metro region. These thunderstorms will be capable of severe winds and a couple of tornadoes along with areas of flash flooding. While the threat for severe thunderstorms looks diminished on Wednesday for the northern Mid-Atlantic region, an increased potential for flash flooding will remain from southern New Jersey into eastern Maryland and the remaining Delmarva Peninsula. The aforementioned cold front and reinforcing shots of cooler air from the north will separate hot and humid conditions over the South from below average temperatures across the Northern Plains. Locations from the Southern Plains to the central Gulf Coast will see heat index values locally over 110 degrees where Heat Advisories are currently in effect. Little relief in the form of thunderstorms is in the forecast for these locations. Farther north however, from Montana and Wyoming to the Upper Mississippi Valley, maximum temperatures are forecast to run 15 to 25 degrees below average on Thursday. Across the Southwest, an continued active monsoon will favor diurnally driven thunderstorms capable of short term high rainfall rates, capable of flash flooding through Thursday. The activity is expected to stretch from as far west as southeastern California to as far east as the central Rockies. In the absence of thunderstorm generated cloud cover, temperatures across the Southwest and much of the western U.S. will continue to run up to 15 degrees above average beneath the influence of upper level ridging centered near the Four Corners region. Otto Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php