Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1204 PM EDT Wed Jul 04 2018 Valid 12Z Sat Jul 07 2018 - 12Z Wed Jul 11 2018 ...Weather threats/highlights.... An upper high will continue to dominate the lower 48 this coming weekend into the middle of next week. Troughs over the Northwest and Northeast flatten with time as a more zonal flow takes shape along the US/Canadian border as heights become above average coast to coast. A moderating front in the east will sink into the Southeast this weekend and dissipate next week as western North American fronts shift downstream across the northern plains, Upper Midwest/Great Lakes and Northeast along with thunderstorm focus and local severe storm threat as per SPC. The Southwest offers potential for record warmth in this pattern, especially this Saturday in southern California where maximum temperatures in the 90s are likely to the coast and well into the 100s inland. Record high minimum temperatures also threaten southern California to southern Arizona this weekend, including Phoenix. ...Guidance evaluation/preferences... The 06 UTC GFS/GEFS, 00 UTC ECMWF, and 00 UTC NAEFS/ECMWF/Canadian ensembles cluster reasonably well with flow evolution days 3-7. The biggest guidance continuity change compared to yesterday is that latest guidance is now more amplified and less progressive with downstream shortwave energy ejection from a mean position off the Pacific Northwest. This adjustment seems to make sense considering the track of a deepened extratropical low associated with the remnants of current west Pacific tropical storm Prapiroon toward Alaska would support this trend to amplify flow downstream into the CONUS. Fracasso/Schichtel WPC medium range 500 mb heights, surface systems, weather grids, quantitative precipitation, winter weather outlook probabilities and heat indexes are found at: http://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif http://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif http://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html http://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml http://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 http://www.wpc.ncep.noaa.gov/heat_index.shtml