Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 359 AM EDT Tue Sep 24 2024 Valid 12Z Tue Sep 24 2024 - 12Z Thu Sep 26 2024 ...Potential Tropical Cyclone Nine is forecast to pass not too far from the Florida Keys Wednesday night as a hurricane before skirting up the West Coast of Florida by Thursday morning... ...Much needed rainfall from the Ohio Valley into the central to southern Appalachians, Upper Tennessee Valley and Mid-Atlantic... ...Much above average temperatures continue across the West into the Northern Plains and across the Gulf Coast into the Southeast... A relatively benign mid- to upper-level trough that will likely bring beneficial rainfall for the eastern U.S. is forecast to deepen when another upper-level trough over the northern Plains drops southeast and merges with the lead trough. The resulting trough amplification will be instrumental in pulling the tropical moisture as well as Potential Tropical Cyclone Nine (PTC9) northward into the eastern portion of the Gulf of Mexico by the end of the short-range forecast period Thursday morning. The initial impacts from the lead trough will be in the form of an expanding area of moderate to heavy rainfall potential from the Midwest into the lower Great Lakes, Ohio Valley, upper Tennessee Valley, central to southern Appalachians into the Mid-Atlantic near and ahead of a low pressure wave. Much of these areas are currently experiencing severe to exceptional drought conditions, with the expected 1 to 1.5 inch plus rainfall amount over the next two days bringing some relief to these drought conditions. With the dry conditions across these areas, river flooding will be unlikely. However, there is still at least a marginal risk of isolated flash flooding with the expected heavy rainfall amounts, especially if they occur over urbanized regions. As the above-mentioned amplifying pattern develops over the northern Plains and dips toward the Deep South, PTC9 is forecast to track more toward the north and intensify rapidly as it moves across the Yucatan Channel on Wednesday and then pass not too far from the Florida Keys Wednesday night. The Florida Keys can expect strengthening winds with more frequent passages of squally downpours Wednesday night as PTC9 is forecast to pass to the west as a hurricane. Computer models indicate that the circulation of PTC9 will expand as it interacts with the deepening upper trough in the Deep South. Given a more robust convective structure concentrated more on the east side of the storm, the West Coast of Florida could begin to see more frequent and intense squalls with winds further strengthening by Thursday morning. Please refer to the National Hurricane Center for the latest updates on this system. The amplifying upper ridge across the interior West will be supporting widespread much above average temperatures over the next few days across nearly all of the West and into the Northern Plains. High temperatures across these regions are forecast to be as much as 10 to 20 degrees above average. Above average temperatures also likely across the Gulf Coast and into the Southeast. While temperatures are forecast to be much above across these areas over the next few days, there are not expected to be many record highs. However, more numerous record high morning temperatures are possible both today and Wednesday morning along the West coast and from portions of the southern Mid-Atlantic into the Southeast and Florida. Across the Pacific Northwest, the cold front associated with a Pacific cyclone centered over the Gulf of Alaska will only bring some rainfall into the region by Wednesday. Kong/Oravec Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php