Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 409 AM EDT Thu Aug 08 2024 Valid 12Z Thu Aug 08 2024 - 12Z Sat Aug 10 2024 ...Debby is forecast to spread excessive rainfall, strong winds and thunderstorms up through much of the Mid-Atlantic/Central Appalachians and Northeast through Saturday morning... ...Excessive Heat concerns continue across the Deep South while cooler air settles over the Central U.S. through the end of the week... ...Monsoonal storms persist over parts of the Southwest, Four Corners and High Plains... Tropical Storm Debby is likely to weaken as it moves from the South Carolina coast and into the Carolina Piedmont tonight before weakening into a Tropical Depression sometime on Friday while it moves up into the Central Appalachians of Virginia, Maryland and Pennsylvania. Debby is expected to produce an additional 4 to 8 inches of rainfall with locally higher amounts, across portions of southeastern North Carolina leading to maximum storm total amounts as high as 15 inches. There's a High Risk (at least 70%) of Excessive Rainfall leading to Flash Flooding from coastal North Carolina, into the Piedmont and up through the Blue Ridge/Appalachians of Virginia. Considerable flooding is expected across portions of eastern South Carolina and southeast North Carolina through Friday. From central North Carolina northward across portions of Virginia, 3 to 7 inches with local amounts to 10 inches, are expected through Friday. This rainfall will likely result in areas of considerable flash and urban flooding, with river flooding possible. From portions of Maryland north through Upstate New York and Vermont, 2 to 4 inches, with local amounts to 6 inches, are expected through Friday night. This will likely result in areas of considerable flash and urban flooding as well as river flooding. There's a Moderate Risk (at least 40%) of Excessive Rainfall over portions of north-central Virginia up through central Pennsylvania/New York for Friday as Debby moves up the spine of the Appalachians. Rain, wind and thunderstorms should come to an end on Saturday when Debby gets swept up into a powerful upper low propagating across southern Canada. Elsewhere, a strong cold front associated with the potent upper low in Canada will drag an anomalously cool airmass down into the mid-section of the country. High temperatures in the 60s and 70s across the Northern/Central Plains and Upper/Middle Mississippi Valley will represent a 15-25 degree negative anomaly for those areas, where some records may be tied or broken. Strong southerly flow beneath a building mid-level ridge will support the continuation of a heat wave from Texas into the central Gulf Coast. Heat Advisories and isolated Excessive Heat Warnings are in effect for those areas. Conditions should improve a bit this weekend following the arrival of the cold front. Monsoonal storms will continue across much of the Southwest, Four Corners and High Plains over the next few days. Diurnal convection along a stalled surface front will promote intense afternoon/evening storms capable of producing heavy rainfall. A Slight Risk (at least 15%) of Excessive Rainfall today and another on Friday are in effect across portions of the Front Range of the Rockies and the Sangre De Cristo/San Juan Mountains. Slot Canyons and burn scars will be most susceptible to flash flooding from any excessive rainfall that occurs. Wildfires in the Northwest will contribute to poor air quality over much of Oregon and western Washington State. Heat Advisories are in effect for western Washington. Kebede Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php