Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 AM EST Tue Nov 15 2022 Valid 12Z Fri Nov 18 2022 - 12Z Tue Nov 22 2022 ***A vast portion of the lower 48 will have daily temperatures that resemble those of January rather than mid-November with widespread subfreezing maximum temperatures expected across the north-central states along with lake effect snow*** ...Synoptic Overview... A highly amplified upper level flow pattern will be in place across the country for the end of the work week with a deep trough extending from Hudson Bay to the Midwest states. An arctic front is progged to reinforce the already very cold airmass that will be in place across the north-central U.S. that is forecast to reach the East Coast in time for the weekend. This trough and accompanying January-like temperatures will likely have some staying power until early next week, when there are signs of a pattern change emerging. The deep trough will likely begin lifting out as a more zonal flow pattern commences across much of the country. Out West, a pacific storm system will likely move inland as the upper ridge axis decays by Sunday and into Monday. ...Guidance and Predictability Assessment... The 00Z deterministic guidance now has an excellent synoptic scale depiction of the broad upper trough over the central-eastern U.S. for Friday and into the weekend with above average confidence at this time frame. The models also agree well on said trough lifting out starting Monday and heralding a pattern change. The greatest models differences are apparent across the Western U.S. going into early next week as a Pacific shortwave approaches the central-northern West Coast region. The CMC is considerably weaker than the GFS/ECMWF for the system reaching the coast Monday, although the CMC shows a stronger shortwave following behind it that is not reflected much in the other guidance. The WPC forecast was primarily based on a multi-deterministic model blend through the weekend, with a gradual increase in use of the EC and GEFS means going into next Monday and Tuesday. For the QPF forecast, particularly in the vicinity of the Great Lakes, the NBM 4.0 solution was too light given the setup for the lake enhanced precipitation, so trended more toward the GFS and ECWMF to increase values. ...Weather/Hazard Highlights... Widespread well below average temperatures for this time of year can be expected across a majority of the country to close out the work week and going into the weekend, with the most impressive readings across Minnesota, North Dakota and Montana where highs will only reach into the 10s Friday through Sunday, and lows within 5 degrees of zero for many of those same areas. Some record low temperatures are possible across portions of the western High Plains, and some record low maximums are also possible across portions of the central Plains to the Upper Midwest behind the next surge of arctic air. It will also be quite chilly extending southward to the Gulf Coast and even much of the Florida Peninsula for at least the first half of the forecast period, with highs generally running 5 to 15 degrees below mid-November averages. Looking ahead to early next week, there will likely be some abatement in the cold weather pattern as the deep upper trough begins lifting out with a more zonal flow evolving. In terms of precipitation, much of the nation should be relatively dry as a sprawling surface high governs the overall weather pattern. Lake effect snow is likely to be persistent downwind of the Great Lakes through Sunday owing to strong cold air advection over the warmer waters, with the heaviest snow expected east of Lake Erie and Lake Ontario where over a foot of accumulation is possible. Showers and mountain snow are likely to make a return to the West Coast states early next week as the Pacific storm system moves inland. Hamrick Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, experimental excessive rainfall outlook, 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/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml