Extended Forecast Discussion NWS Weather Prediction Center College Park MD 229 AM EDT Tue Aug 11 2020 Valid 12Z Fri Aug 14 2020 - 12Z Tue Aug 18 2020 ...Guidance/Predictability Assessment... The WPC medium range product suite was primarily derived from a composite of well clustered guidance from the 12 UTC GFS/ECMWF/UKMET days 3-5 (Fri/Weekend) in a pattern with above normal predictability. Forecast spread and uncertainty gradually increases early next week and the 12 UTC ECMWF seemed the most compatible with 12 UTC GEFS/ECMWF ensemble means. The newer 00 UTC models and ensembles now also seem to reasonably support this overall solution. ...Weather/Hazard Highlights... Surface high pressure dammed down from the Northeast will be slow to erode into the weekend with a closed upper low set to meander near the Canadian Maritimes. A wavy surface front draped back underneath through the Mid-Atlantic to the north-central U.S. and Great Basin will act to focus convection, with guidance showing heaviest rainfall potential over the Mid-Atlantic and north-central U.S./Midwest. Convective potential will be further enhanced as a moderating cold front digs from the north-central U.S. to much of the central and eastern U.S. Fri-next Tue. Possible lead coastal wave development and a weak trailing frontal down through the Southeast/Central Gulf Coast will also focus daily activity. This all occurs as a powerful northern stream upper trough progresses across Canada and the U.S. northern tier. Troughing will also work down into the east-central U.S. early next week as energy increasingly digs to the lee of a summer heat focusing Southwest to Western U.S. building upper ridge. Ridge transition suggests the emphasis for highest max temperature anomalies to plus 10-15F and possible daily records will shift from the southern High Plains to the Desert Southwest over this period. Coverage of above normal temperatures will also expand across the remainder of the West during the weekend into 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