Extended Forecast Discussion NWS Weather Prediction Center College Park MD 201 PM EST Tue Nov 03 2020 Valid 12Z Fri Nov 06 2020 - 12Z Tue Nov 10 2020 ...A significant snow event appears likely for the northern Rockies to the northern High Plains this weekend... ...Tropical downpours and winds associated with Eta could spread northward into southern Florida early next week... ...Overall Synopsis... A major shift in the synoptic pattern is seen in the medium-range period for the western U.S. by the end of the week after an extended period of dry weather and above normal temperatures. A rather pronounced upper level trough will build in across the Intermountain West during next weekend as a widespread significant snow event appears likely from the northern Rockies to the northern High Plains behind an energetic cold front. In contrast, very mild and fine fall weather will continue for the eastern U.S. as a strong upper level ridge remains in control. Meanwhile, tropical cyclone Eta could be tracking farther northward while spreading heavy downpours and winds into southern Florida early next week. ...Guidance Evaluation/Preferences... The WPC prognostic charts were based on a blend of the 00Z EC mean, 06Z GEFS, the deterministic 00Z ECMWF and only a small portion from the 06Z GFS. The 06Z GFS appears to retain too much cyclonic energy for the developing low pressure wave ejecting out from the northern Rockies toward the Canadian prairies on Friday. By the weekend and early next week, the latest runs from the GFS and ECMWF bring Eta much farther north and closer to southern Florida than their previous runs. The CMC and to a lesser degree the UKMet also support such a northern track. The latest NHC track has been adjusted northward as a result. Nevertheless, confidence remains low as model spreads remain significant regarding in the vicinity of the eastern Gulf for early next week. ...Weather/Hazard Highlights... The building western U.S. trough will herald the arrival of much colder temperatures from the Rockies to the West Coast by this weekend, with readings falling at least 25 degrees for many areas compared to highs on Friday. There is a good chance for a significant snow event across portions of the northern Rockies. Maximum temperatures will likely be 10-20 degrees below normal across much of the Intermountain West and the Rockies by Sunday, and lasting into Tuesday. A warming trend is forecast to commence across the central and eastern U.S. ahead of this system, with temperatures that will likely be 10-20F above normal as mid-level high pressure builds across the eastern states. As the trough axis slowly advances eastward over the western High Plains by early next week, moisture interacting with the front could bring locally heavy rainfall to some locations across the central Plains and Midwest. Elsewhere, heavy rainfall is possible across south Florida as moisture interacts with persistent easterly post-frontal flow well to the north of tropical cyclone Eta. Kong/Hamrick 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