Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 AM EST Wed Nov 07 2018 Valid 12Z Sat Nov 10 2018 - 12Z Wed Nov 14 2018 ...Guidance/Predictability Assessment and Weather Highlights/Threats... Recent GFS/ECMWF and GEFS/ECMWF ensemble solutions remain fairly well clustered overall through medium range time scales over much of the nation, bolstering forecast confidence. A composite blend solution that maintains good WPC continuity is suggested. Amplified/dynamic trough passage aloft Saturday from the east-central to northeastern U.S. will support lead surface low and frontal system progression and redevelopment. Exiting precipitation over the Northeast will be enhanced with triple point coastal low genesis. Cooled post-system temps supports wrapback and Great Lake effect snows that spread into the interior northern Mid-Atlantic and Northeast. Showers will linger into next week down over Florida and the Gulf Coast near the trailing stalled front. A storm track to the northeast Pacific/Gulf of Alaska maintains an amplified downstream ridge position along/offshore western North America into early next week. Downstream, a lead northern stream clipper low track and favorable dynamics will squeeze out a swath of snow in cooled air from the north-central states through the Great Lakes/Northeast. Subsequent trough re-amplification aloft back over the central U.S. early-mid next week may be energized by phasing northern and southern stream shortwave impulses digging to the lee of the still amplified but gradually eastward shifting upstream ridge. There is a growing signal supporting ample leading wave/frontal genesis and deep moisture return to would fuel heavy rain/convection expansion northward across the east-central then eastern U.S. Moisture feeding back into a sharpening baroclinic zone meanwhile presents an organized snow threat through the Appalachians/Ohio Valley, with ample lake effect enhancement lee of the Great Lakes and for the interior northern Mid-Atlantic and Northeast with system approach. Significant early season snows are possible. Well upstream, Pacific trough energy and height falls start to work into the Northwest early next week as the lead/amplified ridge aloft gradually/finally shifts inland. This may support an increased chance for precipitation including modest elevation snows. 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