Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1153 AM EDT Sun Aug 05 2018 Valid 12Z Wed Aug 08 2018 - 12Z Sun Aug 12 2018 ...Still Hot for much of the West this Week... ...Pattern Overview and Guidance/Predictability Assessment... The larger scale pattern evolution seems fairly well establlished in guidance. An upper low well west of the Pacific Northwest will move into British Columbia and weaken later this week as the upper high centered over the Great Basin/Southwest attempts to hold in place. Downstream over the east-central U.S., mid-upper level troughing will settle into the region. Forecast spread is manageable over the next week. A composite model and ensemble solution seems a reasonable starting point into day5/Friday. Given increasing forecast spread, prefer an ensemble based solution heading into next weekend and the slightly more amplified 00 UTC ECMWF ensembles compared to GEFS/NAEFS seem a better fit with recent guidance trends and flow history. ...Weather Highlights and Hazards... Well above average temperatures are forecast for much of the West. Some record highs and numerous record warm minimums are likely for the Desert Southwest, Great Basin, and interior Northwest until heights fall and a front pushes ashore next weekend. Light precipitation will be confined to coastal/northern Washington with heavier convective potential in the deeper moisture on the upper diffluent eastern side of the upper high from NM/CO/AZ eastward to the southern Plains. East-central mean troughing will some separation/longevity will meanwhile support periods of heavy convective precipitation that will focus along/ahead of wavy surface fronts and co-driven by warm sector meso-boundaries. Shortwaves and weak surface boundaries will briefly increase coverage of rain/storms through the Great Lakes and Northeast. As the front lingers into the U.S. southern tier and Mid-Atlantic later in the week, the warm/humid airmass will support convection and locally heavy rainfall. Fracasso/Schichtel WPC medium range 500 mb heights, surface systems, weather grids, quantitative precipitation, winter weather outlook probabilities and heat indexes are found 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