Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 501 PM EDT Fri Aug 13 2021 Valid 00Z Sat Aug 14 2021 - 00Z Mon Aug 16 2021 ...Monsoonal thunderstorms expected in the Southwest through the weekend... ...Thunderstorms likely along and ahead of a front from the Central Plains to Ohio/Tennessee Valleys to the Northeast/Mid-Atlantic; severe weather and heavy rain possible ... ...Fred is forecast to impact much of Florida with heavy rain as it moves just west of the Keys on Saturday... ...Oppressive heat continues across the Northwest, Eastern Seaboard, and South-Central CONUS... ...Amended for the latest forecast track of Tropical Depression Fred... A busy weather pattern is in place through the weekend as multiple features set up to the south of a slow-moving upper-level trough stretching from Central Canada into the North-Central U.S. The Southwest Monsoon remains active with showers and thunderstorms anticipated for the next several days as monsoonal moisture continues to flow into the region. Within the last 30 days, portions of the Southwest have received 200-300 percent of average rainfall and thus are vulnerable to additional heavy rain. Accordingly, a Slight Risk of excessive rainfall and Flash Flood Watches cover the southern half of Arizona and New Mexico through Sunday. Farther east, a surface cold front will propagate eastward across the northeastern quadrant of the county, while meandering over the Central Plains/Mississippi Valley. As moisture flows into the front, it should provide a focus for rain and thunderstorms, with both severe weather and flash flooding as possible threats. Today, the greatest chances for severe weather look to be ahead of the front in the Central High Plains, Ohio Valley, and portions of the Mid-Atlantic with Slight Risks delineated by the Storm Prediction Center. Similar to yesterday, scattered damaging wind is anticipated to be the predominant severe threat, and a Severe Thunderstorm Watch currently extends across Maryland into Virginia. Isolated flash floods are also possible today over a large Marginal Risk area stretching from Oklahoma north and eastward toward the Mid-South, Ohio Valley, Great Lakes, and Mid-Atlantic. Then on Saturday, heavy rain looks to focus 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. A few severe thunderstorms could also occur. Meanwhile, Tropical Depression Fred is expected to move across Cuba today while remaining at tropical depression strength. Fred is anticipated to strengthen to a tropical storm and move just west of the Keys on Saturday before turning north into the eastern Gulf of Mexico. Ahead of Fred, bands of tropical showers/thunderstorms are already underway across Florida which could produce isolated flash flooding over South Florida including Miami. As Fred tracks west of the Florida coastline, additional bands of tropical thunderstorms will occur over Florida as deep tropical moisture streams in. Scattered flash floods are possible over South Florida tomorrow, before the flash flood threat expands over much of Florida and Southeast Georgia Sunday as Fred approaches the Florida Peninsula at tropical storm strength. 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. Heavy rain aside, the ongoing oppressive heat continues to be a hazard during the short range period across multiple regions. The Northwest and North Great Basin can expect continued record-breaking heat in terms of both high minimum and maximum temperatures through this weekend. Excessive Heat Warnings and a few Heat Advisories cover much of the Pacific Northwest and Northern Great Basin as temperatures soar into the 100s in the Pacific Northwest and the Northern Great Basin. 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 remain a threat through Sunday as well, which could worsen the ongoing fire situation in the West. In the East, another day of high humidity and hot temperatures creating high heat indices well over 100F is expected, and Heat Advisories are in effect from North Carolina to Maine and also into portions of West Virginia, with Excessive Heat Warnings embedded in the northern Mid-Atlantic. By Sunday, the cooler air behind the passing cold front will break the hot streak and cool temperatures off to around seasonal. Asherman/Tate Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php