Extended Forecast Discussion NWS Weather Prediction Center College Park MD 159 AM EST Mon Nov 14 2022 Valid 12Z Thu Nov 17 2022 - 12Z Mon Nov 21 2022 ***It will feel more like January across much of the U.S. with widespread subfreezing high temperatures expected across the north-central states along with lake effect snow*** ...Synoptic Overview... A rather cold pattern is expected to be in place across much of the nation for the end of the week into next weekend with broad cyclonic flow aloft around a deep upper level trough centered near the north-central U.S. and extending to Hudson Bay. Multiple reinforcing cold fronts/shortwaves will help to maintain this pattern, and a strong upper ridge axis should prevail just off the West Coast through Saturday before breaking down some. A well organized storm system will be crossing southeast Canada on Thursday, with coastal rain and inland snow expected, followed by lake effect snow downwind of the Great Lakes ...Guidance and Predictability Assessment... The 00Z model guidance suite is in good synoptic scale agreement for the Thursday-Friday time period and agree on a strong reinforcement of the arctic air mass across much of the northern tier states. The latest ECMWF has trended closer to recent runs of the GFS with respect to a potential storm system off the Southeast Coast with not much phasing of southern/northern stream energy, with a weaker system and less precipitation inland like its 12Z run had. The WPC forecast was primarily based on a multi-deterministic model blend through about Friday, followed by increasing the inclusion of the GEFS and EC ensemble means to account for the greater model differences going into the weekend. In terms of QPF, a blend of about 20% GFS/20% GFS/60% NBM 4.1 was used as a baseline for the Great Lakes region to add more detail to the expected lake effect snowfall, and then increased slightly above that. ...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, with the most impressive readings across North Dakota and Montana where highs will only reach into the 10s and overnight lows likely falling below zero by Friday morning. 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 10-20 degrees below mid-November average. Looking ahead to next Monday, there may be some abatement in the cold weather pattern as the deep upper trough begins to show signs of finally lifting out across the central U.S. 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 owing to strong cold air advection over the warmer waters, with the heaviest snow expected east of Lake Erie and Lake Ontario. Some snow showers are also likely across portions of the Rockies as a weak disturbance drops southeastward, but nothing major expected there. There is a bit more uncertainty regarding the potential evolution and track of a wave of low pressure over the Gulf that could bring light to moderate rain for the Gulf Coast region and the interior Southeast by the weekend, so this will continue to be closely monitored. 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