Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 414 PM EDT Thu Aug 05 2021 Valid 00Z Fri Aug 06 2021 - 00Z Sun Aug 08 2021 ...Heavy rainfall and the chance for flooding continues for portions of the Southeast along a persistent frontal boundary... ...Showers and storms likely for the Northern Rockies and High Plains on Friday... ...Heavy rainfall possible for the Midwest with severe weather expected Saturday... Showers and storms continue this afternoon across parts of Florida along a persistent, quasi-stationary frontal boundary draped across the northern half of the Peninsula and just off the East and Gulf Coasts. This boundary will slowly move back to the north onshore the coastal Carolinas, Georgia, and Gulf Coast over the next couple of days. Waves of low pressure along the boundary as well as an upper-level trough moving east across the region will help encourage widespread shower and thunderstorms along the boundary. A Slight Risk of excessive rainfall (level 2 of 4) remains in effect for the Big Bend of Florida through tomorrow morning for the chance of 3 to 5 more inches of heavy rainfall. A Marginal Risk (level 1 of 4) is in effect for a broad portion of the Southeast on Friday as well as for portions of the eastern Carolinas on Saturday. Areal average rainfall of 1 to 2 inches may lead to a few localized instances of flooding, especially for places that have already seen heavy rain the past few days. A upper-level trough from the Pacific will move east over the Northern Rockies through the day Friday. Showers and storms are likely for the Northern Rockies and High Plains as a low pressure system develops in the lee of the Rockies and a cold front develops and moves east across the region. A Marginal Risk of excessive rainfall is in effect for Friday as some of the heavier downpours could lead to localized instances of flash flooding, particularly across areas of steeper terrain and any burn scars. In the Midwest, a pair of upper-level troughs will move across the area through the period. A cold front will move through the Upper Great Lakes on Friday with the first trough as the storm system over the Northern Rockies approaches from the west with the second trough on Saturday. A Marginal Risk of excessive rainfall is in effect on Friday for the first round of storms, with locally heavy rainfall of up to an inch possible. As the second storm system approaches, a warm front will lift north across the Upper Mississippi Valley, advecting moist, buoyant air across the region ahead of a cold front moving in from the west across the Dakotas. The Storm Prediction Center has issued a Slight Risk (level 2 of 5) of severe weather on Saturday centered around southern Minnesota and northwestern Iowa. Both supercells and organized clusters of storms are expected to develop with a risk of hail and high winds, as well as the chance for a brief tornado. A Marginal Risk of excessive rainfall is also in effect for Saturday as heavy rain is possible with these storms, although the greater threat for heavy rain may be overnight Saturday just after the end of the current forecast period. Elsewhere, generally mild conditions for August are expected. High temperatures below normal are likely across the Southeast due to persistent clouds and storms as well as behind the cold front in the Northwest, with highs near to a bit above normal in the Northeast. The relatively hottest weather is expected across the Central High Plains with highs in the upper 90s to 100 degrees forecast. Poor air quality due to wildfire smoke from the West looks to remain an issue, particularly for portions of the Northwest, the High Plains, and the Upper Midwest. Putnam Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php