Extended Forecast Discussion NWS Weather Prediction Center College Park MD 248 AM EDT Wed Aug 12 2020 Valid 12Z Sat Aug 15 2020 - 12Z Wed Aug 19 2020 ...Much above normal temperatures offer a threat of record temperatures for a dry West... ...Guidance/Predictability Assessment... The WPC medium range product suite was derived from a composite of clustered guidance of the 18 UTC GFS/GEFS mean, 12 UTC ECMWF/ECMWF ensemble mean and 02 UTC National Blend of Models Sat-Tue in a pattern with above normal predictability. Forecast spread does increase by next midweek, but the ensemble means remain compatible. ...Weather/Hazard Highlights... High pressure dammed down from the Northeast will be slow to recede this weekend with a closed upper low meandering over the Canadian Maritimes. A wavy front draped back underneath through the Mid-Atlantic to the north-central U.S. will act to focus convection, with guidance showing heaviest rainfall potential over the Upper OH Valley, Central Appalachians and Mid-Atlantic. Convection will also be enhanced as a moderating cold front digs robustly from the north-central U.S. through much of the central and eastern U.S. Sat-next Wed. Weak lead coastal wave development and a weak trailing front through the Southeast should also focus daily activity. This all occurs as a powerful northern stream upper trough progresses across Canada and the U.S. northern tier. Ample troughing will also work far down into the east-central U.S. next week as energy increasingly digs well to the lee of a high heat focusing Southern Plains then Southwest to Western U.S. upper ridge. Ridge position will inhibit monsoonal onset. Emphasis for highest max temperature anomalies of 10-15F+ offers record values for the Desert Southwest where hottest temperatures will exceed 115 degrees. Much above normal temperatures with additional record values also spreads over the rest of the West in tandem with upper trough amplification off the West Coast. A dry pattern with frontal relief possible only for the Pacific Northwest into next midweek. 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