Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 PM EDT Fri Aug 13 2021 Valid 12Z Mon Aug 16 2021 - 12Z Fri Aug 20 2021 ...Heavy rain associated with Tropical Storm Fred expected to spread further inland into the Southeast early next week... ...Potential Tropical Cyclone Seven could approach Florida during the latter half of next week... ...Pattern Overview... An upper level trough will likely move through the Northwest during the early part of next week before reaching the northern Plains later next week, heralding the end of the ongoing heat wave across the region. Meanwhile, Tropical Storm Fred is forecast to make landfall on the eastern Gulf Coast early next week and spread heavy rainfall inland across the Southeast U.S./southern Appalachians into midweek. Toward the latter half of next week, Potential Tropical Cyclone Seven is forecast to intensify into a tropical storm and approach Florida. ...Guidance/Predictability Evaluation... Models and ensemble means are in very good overall agreement on the pattern change expected across the north-central U.S. through the beginning of the week. Deterministic models become more divergent toward the end of next week regarding whether a low pressure wave will develop and intensify over the northern Plains. A general model compromise with increasing weights towards the ensemble means on Days 6 and 7 yielded a solution fairly close to continuity. This is also true regarding the remnants of Fred across the Southeast with the ECMWF still favors more QPF pushing north into the southern Appalachians. ...Weather Highlights/Hazards... The ongoing heat wave over the Northwest is expected to be over by Monday with temperatures returning to near normal levels. Some portions of the Northern Rockies and adjacent portions of the northern Plains could be 10 to 20 degrees below normal next Tuesday into Wednesday. High are expected to be above normal ahead of the cold front across the northern Plains on Monday, followed by more pleasant readings by midweek. Tropical moisture is expected to lift northward across interior portions of the Southeast and southern Appalachians after Fred makes landfall, potentially interacting with a stalled frontal boundary and terrain enhancement. Exact locations of heaviest rainfall depends on the eventual track of Fred, and this is subject to additional changes in future forecasts. Elsewhere, monsoon activity over the Desert Southwest should increase and spread northward, again bringing a localized flash flood risk. Moisture should stream northward ahead of the incoming trough into the Northwest, with a potential for moderate to heavy rainfall emerging over parts of the northern Rockies/high Plains on Tuesday, with organized and enhanced rainfall then focusing along the cold front as it advances across the Northern Plains Tuesday into Wednesday. Kong/Hamrick Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, winter weather outlook probabilities and heat indices are at: https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml