Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1205 PM EDT Fri Jul 03 2020 Valid 12Z Mon Jul 06 2020 - 12Z Fri Jul 10 2020 1600 UTC Update... Overall, models/ensembles continued to show relatively good consensus at larger scales through much of the extended forecast period, but with increasing differences at smaller scales by later in the forecast period. Thus, no major changes were made to the ongoing forecast with this update. The forecast was updated to incorporate some of the latest model guidance, including the 00Z ECMWF and 06Z GFS. A heavily deterministic blend was used during days 3-4 (Mon-Tue), with a shift to gradually more emphasis placed on ensemble means (00Z ECENS/06Z GEFS) through time during days 5-7 (Wed-Fri). The GFS was removed from the forecast blend after day 5, as it became significant faster than consensus with shortwave energy reaching the Pacific Northwest during days 6-7. Meanwhile, the ECMWF was a bit slower than consensus, supporting the increased emphasis on ensemble means during that time period, which showed somewhat better consensus. Ryan Previous Discussion (issued at 0700 UTC)... ...Guidance/Predictability Assessment... Models and ensembles offer a reasonably similar large scale pattern evolution, but have increasingly problematic differences with smaller scale impulses and convection over time. This is not uncommon for the summer. To mitigate these issues and considering recent skill, the WPC medium range product suite was primarily derived from a blend of the generally compatible 18 UTC GFS/GEFS mean and the 12 UTC ECMWF/ECMWF ensemble mean along with the 01 UTC National Blend of Models. Leaned WPC blend weighting toward the GFS and especially the ECMWF early-mid next week and then the GEFS mean and especially the ECMWF ensemble mean mid-later next week. This forecast strategy seems to best address growing forecast spread and the resultant solution maintains good WPC continuity in line with newer 00 UTC guidance. ...Weather Pattern/Hazard Highlights... Unsettling Pacific upper trough energies will work inland over the Northwest next week. A steady diet of ejecting impulses will progress downstream over southern Canada and the U.S. northern tier. This will force a series of moderating fronts across the region and spawn periods with strong instability/convection and locally heavy downpours/runoff issues. Potential may focus from the northern Rockies/Plains to the Upper Midwest. Lead flow and mean upper ridging may bring the most anomalous heat over the Midwest/Northeast. Elsewhere, triple digit maximum daytime temperatures will focus from the Desert Southwest/southern Great Basin to the south-central Plains and hot and humid weather (including some record warm overnight temperatures will rule south of these fronts over the central and eastern U.S. Some heavy convective downpours/local runoff issues may focus into the South/Southeast/Mid-Atlantic near a slow moving mean trough aloft and wavy/slow moving frontal drape. 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