Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Mon Oct 19 2020 Valid 12Z Thu Oct 22 2020 - 12Z Mon Oct 26 2020 ...Guidance Evaluation/Preferences... The WPC medium range product suite was primarily derived from a composite blend of reasonably well clustered guidance of the 18 UTC GFS/GEFS mean, 12 UTC ECMWF/ECMWF ensemble mean and the 01 UTC National Blend of Models Thursday-Saturday. Shifted blend emphasis to mostly the still compatible ensemble means Sunday-next Monday as consistent with growing forecast spread and uncertainty. ...Weather/Hazard Highlights... There is a good guidance signal showing that amplified upper trough energy over the West Thursday will eject over the north-central and northeast U.S. Friday into the weekend as potent upstream kicker trough energies dig sharply down into the West. A lead frontal system will focus some periods of moderate precipitation from the northern Rockies and north-central U.S./Midwest to the Northeast. Post-frontal Canadian cold air will dig through the Northwest/Great Basin and the central to eastern U.S. There is also a subsequent signal showing the carving out of a more amplified upper trough over the West Fri through the weekend/Mon. This may prove to support ample cooling and unsettled/wet conditions down over much of the West and allow the lead spilling of post-frontal cold Canadian air downstream through the central U.S. in the wake of uncertain but potentially deep cyclogenesis. Temperature profiles in this pattern favors periods of snow for the cooled northern Rockies and north-central states. The highest chance of heavy snows remains for the northern Rockies. The heaviest rains may meanwhile focus over the Midwest/Great Lakes with frontal wave genesis/passage. Lead moisture and moderate rains will be also be pulled northward across the Southeast in advance of the lead aforementioned system. Farther south, moisture may additionally increase over Florida and the east-central Gulf states late week as a tropical low is forecast to move slowly northward from the western Caribbean Sea. 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