US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 443 PM EDT Thu Aug 26 2021 Valid Sunday August 29 2021 - Thursday September 02 2021 Hazards: - Heavy rain across portions of the Southeast, the Middle Mississippi Valley, the Lower Mississippi Valley, the Southern Plains, and the Tennessee Valley, Sun-Mon, Aug 29-Aug 30. - Heavy rain across portions of the Central Plains, the Middle Mississippi Valley, the Upper Mississippi Valley, and the Northern Plains, Mon, Aug 30. - Heavy rain across portions of the Lower Mississippi Valley, the Central Appalachians, the Tennessee Valley, the Middle Mississippi Valley, the Mid-Atlantic, the Southern Appalachians, the Southeast, and the Ohio Valley, Tue-Wed, Aug 31-Sep 1. - Heavy rain across portions of the Southwest, Wed-Thu, Sep 1-Sep 2. - Flooding possible across portions of the Great Lakes and the Upper Mississippi Valley. - High winds across portions of the Southeast, the Lower Mississippi Valley, and the Southern Plains, Sun-Mon, Aug 29-Aug 30. - High significant wave heights for coastal portions of the Southeast, the Lower Mississippi Valley, and the Southern Plains, Sun, Aug 29. - Heavy rain across portions of mainland Alaska, Thu, Sep 2. Detailed Summary: The track and resulting hazards generated by Tropical Depression Nine is the headliner through at least the first half of the medium range period (Sunday, Aug 29 - Thurs, Sept 2). Tropical Depression Nine is forecast to organize and strengthen over the next 24 hours and make landfall in northwest Cuba late Friday. It will enter the Gulf of Mexico tracking northwest while encountering light levels of vertical wind shear and passing over the very warm waters. The stage is set for T.D. Nine to rapidly intensify, perhaps all the way up until landfall, along the central Gulf Coast. Latest ensemble guidance has become more clustered over the central Louisiana coast, but some members are as far west as the Upper Texas coast or as far east as Mobile Bay. There is still some uncertainty regarding exact landfall, which not only varies by location but also timing. Some guidance suggests landfall could be Sunday afternoon or some time Monday night. Regardless, the expectation is for a dangerous hurricane to take aim at the Louisiana coast bringing life threatening hazards to parts of the central Gulf Coast and into the Lower Mississippi Valley. Hazards will vary depending upon intensity and track with areas just north and east of the storm most at risk for greater impacts. Life threatening storm surge and inland flooding is possible ahead of and just east of the storm's expected track. Rainfall totals exceeding 12 inches are anticipated somewhere along the central or eastern Louisiana coast with torrential rainfall rates potentially leading to dangerous flash flooding into south-central Louisiana. Destructive hurricane force winds will be focused along the coast and a little further inland, or so long as the storm can maintain hurricane strength. As the storm pushes further inland, so will its tropical storm force wind field where a swath of wind damage is likely to include (but is not limited to) downed trees, power lines, and structural damage to homes and businesses. Also, northeast of the storm's track will likely contain a severe weather threat as tornadoes may develop across parts of the Deep South late Sunday into Monday. Eventually, the flood threat becomes the primary hazard of note by Tuesday and Wednesday as T.D. Nine's remnant tropical moisture becomes focused along a frontal boundary inching south through the Tennessee Valley, southern and central Appalachians, and Mid-Atlantic. Specific locations in these regions have received heavy rainfall and dealt with areas of flash flooding in recent weeks, so rainfall on the order of 2-5 inches could promote additional flash flooding concerns in these areas. Please visit the NHC website for the latest track and intensity forecast information in the days to come and follow the advice of local officials for those in the path of T.D. Nine. There is another tropical system that could also leave its mark on the U.S., more specifically in the Southwest. Tropical Storm Nora is forecast to strike the Baja California peninsula and weaken as it tracks north early next week. Its remnant moisture will be transported north ahead of an upper trough diving into the Pacific Northwest. Latest 12Z Euro ENS mean has PWATs nearly 2 STDs above normal out to days 5-6 in the Four Corners region. Guidance remains unclear as to when the heaviest rounds of showers and thunderstorms pass through Arizona and into the heart of the Four Corners region, but ample moisture courtesy of Nora could lead to areas of heavy rainfall and flash flooding in parts of the region next week. Also, another round of heavy rainfall within a cluster of thunderstorms is possible in parts of the North Central U.S. late Monday into early Tuesday just north of a warm front forecast to track into the region. Localized flash flooding is possible in the highlighted area of the Midwest. Over Alaska, the start of September looks stormy as another occluded storm system is expected to impact the state, this time generating moderate to heavy rainfall over the Aleutians, east towards the upper Peninsula, and along the west-central Gulf coast. Roughly 2 to 3 inches of drenching rain is possible for the southern coastal portion of the upper Peninsula, Kodiak Island, the Kenai Peninsula, and areas surrounding the Cook Inlet. There may also be some gusty winds It is possible for heavy rainfall to extend farther east along the eastern half of the Gulf coast and potentially towards the northern Panhandle by day 7, but confidence in totals and timing is low at this time. Temperature-wise, a more autumn-like start to the period on Sunday gradually warms up into next week to more seasonal levels by mid-week. Mullinax