Extended Forecast Discussion NWS Weather Prediction Center College Park MD 228 AM EDT Sat Oct 31 2020 Valid 12Z Tue Nov 03 2020 - 12Z Sat Nov 07 2020 ...Heavy Precipitation for the Pacific Northwest... ...Overview... An anomalously strong and cold upper trough ejects from New England Tue as fast zonal flow develops upstream over the CONUS. Upper trough amplification offshore the Pacific Northwest next week will direct deep moisture into western WA. There is a good signal for a heavy precipitation focus in the Olympics/Cascades by Tue/Wed, with lowering snow levels before shifting into OR/CA and the northern Rockies later next week as the vigorous upper trough/height falls work inland over the West. Otherwise, dry conditions will prevail for much of the rest of the lower 48 except for parts of FL in protracted easterly post-frontal flow well to the north of yet another potential Caribbean tropical system being monitored for development by the NHC. ...Guidance Evaluation/Preferences... The WPC medium range product suite was primarily derived from a composite blend of the latest and well clustered solutions from the GFS/ECMWF, GEFS/ECMWF ensemble means, the National Blend of Models and WPC continuity in a pattern with above normal predictability near the lower 48 day 3 into 7. ...Weather/Hazard Highlights... Cold air may threaten some temperature records in the Northeast into Tue as lake enhanced snows linger downwind of Lake Ontario. Below normal temperatures over the East will moderate in the first half of the week as the above normal temperature across The West expand east to the Plains/Midwest/Northeast. Some records are possible over CA/AZ. Heaviest precipitation is expected over the Pacific NW, particularly WA Tue/Wed as fueled by an atmospheric river. Rains and lowering elevation snows will spread over the Northwest to the Northern Rockies and north-central CA/Great Basin later next week. Rainfall potential also increases into FL next week in easterly fetch well to the north of another possible Caribbean tropical system. 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