US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 348 PM EDT Thu Aug 12 2021 Valid Sunday August 15 2021 - Thursday August 19 2021 Hazards: - Heavy rain across portions of the Upper Mississippi Valley and the Northern Plains, Wed-Thu, Aug 18-Aug 19. - Heavy rain across portions of the Southeast, Sun-Mon, Aug 15-Aug 16. - Heavy rain across portions of the Southeast, the Southern Appalachians, the Mid-Atlantic, the Central Appalachians, and the Tennessee Valley, Mon-Wed, Aug 16-Aug 18. - Heavy rain across portions of the Southwest, Sun-Tue, Aug 15-Aug 17. - Flooding possible across portions of the Southeast. - Flooding occurring or imminent across portions of the Southeast. - Flooding likely across portions of the Southeast. - Excessive heat across portions of the Central Great Basin, the Northern Plains, the Northern Rockies, California, the Northern Great Basin, and the Pacific Northwest, Sun, Aug 15. - Excessive heat across portions of the Central Plains, California, the Northern Plains, and the Southwest, Sun-Mon, Aug 15-Aug 16. - Heavy rain across portions of mainland Alaska, Mon, Aug 16. - Heavy rain across portions of the Alaska Panhandle and mainland Alaska, Tue-Wed, Aug 17-Aug 18. Detailed Summary: The medium range forecast period (Sunday, August 15 to Thursday, August 19) features multiple areas at risk of heavy rain or excessive heat. Starting in the southeastern United States, Tropical Depression Fred is currently forecast to slightly strengthen and regain tropical storm strength near the Florida Gulf Coast on Sunday before pushing inland near the Georgia and Alabama border on Monday. As a result, heavy rain is possible near and to the east of the center due to the expected unorganized structure of Fred over North Florida and portions of the Southeast through Monday. Farther north, an approaching cold front may draw tropical moisture into the southern Appalachians and Mid-Atlantic early next week. Uncertainty regarding the highlighted heavy rainfall areas and exact rainfall amounts remains higher than average due to Fred's disorganization, but regardless of Fred's future, heavy rain near and ahead of the approaching cold front could lead to isolated flooding concerns. Otherwise, a separate tropical disturbance and a feed of rich atmospheric moisture may impact southern Florida with heavy rain by next Thursday. A highlighted area was not added to today's graphic, but may be needed with future updates as the tropical forecast becomes clearer. As always, be sure to check with the National Hurricane Center for the latest tropical cyclone forecasts and outlooks. Elsewhere, heavy rain is also expected to impact drought-stricken regions of the Southwest and Northern Plains/Upper Midwest. Monsoonal showers are expected to continue producing scattered downpours over southern Arizona and New Mexico through at least Tuesday. That is when an associated retrograding upper-level low is forecast to exit into the western Pacific with the remaining atmospheric moisture escaping to the north and into the central Great Basin ahead of an approaching upper-level trough. As a result, the heavy rain threat may expand into central and northwest Arizona, as well as far southwest Utah by early next week. For the Northern Plains and Upper Midwest, this section of the country is currently experiencing widespread extreme to exceptional drought, but some relief is on the way. An approaching cold front could spark numerous showers and thunderstorms beginning midweek. Scattered rainfall amounts great than 1 inch are possible. The biggest uncertainty regarding this highlighted rainfall area involves timing and how far south the heavy rain extends. Excessive heat will also remain a concern while gradually diminishing for parts of the north-central and western U.S. through Monday. Sunday and Monday will be the tail-end of yet another heat wave for this part of the country. Temperatures 10 to 15 degrees above average with highs approaching the century mark are forecast across the Great Basin and central Montana on Sunday, before much cooler temperatures arrive on Monday and Tuesday. However, dangerous heat will linger one additional day throughout the high deserts and San Joaquin Valley of California, as well as the northern High Plains. By the middle of next week the only area with potentially oppressive heat will be found across South Texas and the western Gulf Coast. High temperatures in the mid-to-upper 90s will be close to normal for this time of year, but heat indices around 110 degrees and low temperatures only dropping into the 80s can be dangerous if proper heat safety is not followed. For Alaska, a low pressure system and associated frontal boundaries will produce chances for heavy rain along and south of the eastern Brooks Range on Sunday and Monday. The greatest chances for heavy rain will be on Monday as a plume of moisture moves inland from the Bering Strait. Heavy rain is also a possibility over the Alaska Panhandle and south-central portions of the state on Tuesday and Wednesday. Rainfall amounts are expected to be much lower than the current atmospheric river event, but areas of 2+ inches seem plausible throughout northern parts of the panhandle. Snell