Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1150 AM EDT Thu Jul 12 2018 Valid 12Z Sun Jul 15 2018 - 12Z Thu Jul 19 2018 ...Overview and weather highlights... Troughing is forecast to ease into the northeast portion of the lower 48 next week which will carry a surface front out of the Plains and through the Mid-Atlantic states. Temperatures will be near to above average (anomalies about +5 to +15F) ahead of this boundary with some isolated record highs possible in an otherwise typically hot summertime regime. The cold front will bring in drier and slightly cooler air in its wake (anomalies about -5 to -10F), first to the High Plains late this weekend then to the Midwest and Northeast later in the week. Precipitation will follow along the path of the front with scattered showers/storms over the Southeast and interior west with a decrease in time over the Four Corners region as upper ridging strengthens. ...Guidance evaluation and preferences... Models/ensembles show good agreement overall with much of the timing differences confined to the higher latitudes north of the US/Canadian border. However, run-to-run consistency remains a bit lackluster and confidence in the details after Tuesday next week were average at best. Problems stem from short range uncertainty over Alaska that carries into Western Canada early in the period that set the stage for the troughing in the east Tue-Thu. Recent 00Z/06Z GEFS ensembles and ECMWF ensembles have somewhat converged over the Midwest/Great Lakes by next Wed/Thu (at least compared to the 12Z runs from yesterday) so a blend among the deterministic GFS/ECMWF and their ensemble means was usable through the period. This resulted in a quicker frontal progression through Canada and the east Tue-Thu but otherwise maintained continuity. Fracasso 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