Extended Forecast Discussion NWS Weather Prediction Center College Park MD 259 AM EDT Thu Oct 01 2020 Valid 12Z Sun Oct 04 2020 - 12Z Thu Oct 08 2020 ...Hot and dry conditions across The West expand into the central U.S. next week... ...Heavy rainfall threat for the Florida Peninsula through next midweek... ...Overview and Guidance/Predictability Assessment... Guidance overall favors reinforcement of a central to eastern U.S. upper trough position Sunday/Monday as energy digs to the lee of an amplified western North American upper ridge, then out through the Northeast/western Atlantic Tuesday. Models and ensembles differ with the extent of amplification/stream separation within the mean upper trough. The GFS/GEFS are quicker to flatten the ridge into next week and are more progressive/less amplified with this downstream upper trough than the ECMWF ensemble mean and especially the ECMWF. In this case, I'd prefer a solution on the more amplified side of the full envelope of solutions closest to the ECMWF ensemble mean. Water vapor imagery shows quite a vigorous shortwave now to the north of Hawaii that is slated by guidance to lift robustly north to Alaska into the weekend. This should favor ample downstream ridge amplification over western Canada, likely most in line with the ECMWF ensemble mean. The ECMWF ensemble mean and GEFS ensemble mean seem in closer agreement later into days 6/7 and offer a seemingly reasonable flow evolution toward a somewhat less amplified west-central U.S. upper ridge and downstream upper trough pattern. ...Weather/Hazard Highlights... Upper trough instability and wavy frontal translation/focus will provide unsettled conditions and moderate rain potential from the Midwest/Great Lakes through the Ohio Valley and Northeast. A stalling trailing front over the Florida Peninsula will focus a major threat of multi-day heavy rainfall and runoff issues through this period. Activity will be fueled by the influx of deep tropical moisture from the Caribbean where several disturbances are being monitored by NHC. The upper ridge persisting across The West continues to offer hot and dry conditions with associated fire risks. Expect temperatures 5-15 degrees F above normal from the Desert Southwest up through the and Northwest Sunday to expand east to the central/southern Plains next week. A few record high temperatures are possible. Alternately, a reinforcing cold air surge this weekend will keep temperatures of 5-15 degrees F below normal for much of the central to eastern U.S. Sunday before moderating as it shifts southeast with the cold front early next week. Schichtel Additional 3-7 Day Hazards information can be found on the WPC medium range hazards 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