Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 PM EST Sat Nov 12 2022 Valid 12Z Tue Nov 15 2022 - 12Z Sat Nov 19 2022 ...Much below normal temperatures to settle over much of the nation along with a threat for Appalachians/Interior Northeast and Great Lake Effect Snows... ...Synoptic Overview... A rather cold pattern is expected to be in place across much of the nation for next week with broad cyclonic flow aloft around a deep upper level trough centered near the north-central U.S. and extending into central Canada. Multiple reinforcing cold fronts/shortwaves will help to maintain this pattern, and a strong upper ridge axis should prevail just off the West Coast. There will likely be two separate Gulf Coast storm systems that develop in response to shortwaves tracking around the southern periphery of the deep trough, and these are expected to produce rounds of rain from the Deep South to the East Coast. The cold air will also favor swaths of enhanced snow/ice on the western periphery of the associated precipitation shield from the central to the northern Appalachians/interior mountains of the Northeast. This pattern will also favor a protracted opportuniuty for periods of lake enhanced snows to the lee of the Great Lakes. ...Guidance and Predictability Assessment... Models and ensemble solutions overall seem well clustered Tuesday/Wednesday for much of the lower 48 states, bolstering forecast confidence in a composite solution to mitigate lingering smaller scale variance. Guidance differences become increasingly evident through the remainder of next week, especially over the West where the 00/06 UTC GFS and 00 UTC Canadian dug much more ample upper trough/low energies in separated flow than the 00 UTC ECMWF and GEFS/ECMWF ensembles. The 12 UTC GFS has completely flipped to focus most upper energies into the central U.S., but the 12 UTC Canadian has not changed continuity and incredibly now the 12 UTC ECMWF has dramtically switched to show much more upper troughing over the West. The WPC medium range product suite was primarily derived from the 06 UTC GEFS and 00 UTC ECMWF ensemble means given greater than normal pattern evolution uncertainty. This still seems supported by the 12 UTC GEFS. With respect to targeted changes to 13 UTC NBM QPF, WPC QPF increased amounts to the lee of the Great Lakes in quite favorable flow next week and also favored potential for modestly more amounts for the Gulf Coast/Southeast considering organization of the main two supporting lows/frontal systems expected to traverse the region this period. ...Weather/Hazard Highlights... Two organizing system near the Gulf Coast early and then later next week are expected to lift northeastward and produce moderate swaths of rain across much of the South and Southeast. Lead system track and coastal low transition up the East Coast midweek also offers a threat for enhanced snow/ice on the western periphery of the associated precipitation shield from the central to the northern Appalachians/interior mountains of the Northeast. Northern stream energy passages and cold air advection over the Great Lakes is expected to produce Great Lake effect snow at times, and some of this snow could be locally heavy in a reinforcing cold flow pattern for much of next week. The other noteworthy aspect of the extended forecast will be the widespread anomalous cold weather across a great deal of the nation for basically all of next week, especially from the unsettled interior West to the High Plains/Midwest where temperatures may run 15-30 degrees below mid-November averages. Some spotty daily records are also possible. Exceptions to the cold weather may be the Florida Peninsula and possibly the West Coast, with readings near or slightly above average. Hamrick/Schichtel 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