Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 AM EDT Sat Aug 14 2021 Valid 12Z Sat Aug 14 2021 - 12Z Mon Aug 16 2021 ...Monsoonal thunderstorms could cause scattered flash flooding in the Southwest through the weekend... ...Thunderstorms likely along and ahead of a front from the Plains to Ohio/Tennessee Valleys to the Mid-Atlantic, with strong storms and flash flooding possible ... ...Fred is forecast to impact much of Florida with heavy rain as it moves just west of the Keys today... ...Oppressive heat continues particularly across the western U.S. with one more warm day along the Eastern Seaboard as well... A busy weather pattern is in place through the weekend as multiple features set up to the south of a typical summer jet stream focused along the northern U.S. and Canada. One area of concern is the Southwest, as showers and thunderstorms are once again forecast as above normal monsoonal moisture continues to flow into the region. A wet monsoon season has meant much of the Southwest has seen 200-300 percent of its average rainfall and thus is vulnerable to additional heavy rain. Accordingly, Flash Flood Watches cover the southern half of Arizona, parts of New Mexico, and Far West Texas through Sunday, with a Slight Risk of excessive rainfall also in place today. Farther east, a surface cold front will propagate eastward across the northeastern quadrant of the county today, while meandering over the Plains and Mississippi/Tennessee Valleys through Monday. As moisture flows into the front, it should provide a focus for rain and thunderstorms, with flash flooding and possibly severe weather as threats. Isolated flash floods are possible across much of the south-central and southeastern U.S. through Monday, with broad Marginal Risk areas outlooked for excessive rainfall. Today into tonight, rainfall totals could be enhanced over portions of the Mid-Atlantic, and especially given the wet antecedent conditions, scattered flash floods are possible and a Slight Risk of excessive rainfall is in place. Some strong to severe storms also could occur in a few areas along the frontal system today where the Storm Prediction Center has Marginal Risk areas in place--the Central High Plains, the Mid-Atlantic, and New England. Meanwhile, Tropical Depression Fred is currently expected to move west-northwest and pass near or west of the lower Florida Keys later today, move into the eastern Gulf of Mexico by Sunday, and move inland over the Florida Panhandle on Monday. Slow strengthening of the system is forecast, and Fred could once again become a tropical storm before landfall. Users are encouraged to follow the latest forecast information from the National Hurricane Center, as Tropical Storm Warnings are in effect for the Florida Keys and areas offshore Southwest Florida. While gusty winds are a threat with Fred, additionally, heavy tropical downpours could cause scattered flash flooding over much of Florida through the weekend associated with the system. A Slight Risk of excessive rainfall is in place for southern Florida through the weekend, while portions of the Florida Panhandle are added to the Slight Risk Sunday as Fred approaches. Heavy rain aside, the ongoing oppressive heat continues to be a hazard during the short range period, especially across the West. Excessive Heat Warnings and some Heat Advisories cover much of the Pacific Northwest, the Great Basin, and California as temperatures soar into the 100s. This heat could be record-breaking once again in terms of both high minimum and maximum temperatures. The heat is forecast to lessen somewhat at least in the Seattle and Portland areas by Sunday, but the interior will remain hot, and above normal temperatures are expected to spread toward the Northern Plains to begin next week. In addition to the heat, Air Quality Alerts are in place for the Northwest and into parts of the Rockies given smoke from fires and high ozone levels. Unfortunately, isolated dry thunderstorms and Elevated to Critical fire conditions remain a threat through at least Sunday as well, which could worsen the ongoing fire situation in the West. Meanwhile, temperatures are expected to be warmer than normal today across the Eastern Seaboard ahead of the cold front, and warm minimum daily records could be set this morning with high heat indices once again this afternoon. However, by Sunday, temperatures should be near to below normal behind the cold frontal passage. Tate Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php