Extended Forecast Discussion NWS Weather Prediction Center College Park MD 156 AM EST Fri Dec 02 2022 Valid 12Z Mon Dec 05 2022 - 12Z Fri Dec 09 2022 ...Guidance and Predictability Assessment... The WPC medium range product suite was primarily derived from a composite of reasonably well clustered guidance from the 18 UTC GFS and 12 UTC ECMWF/UKMET/Canadian models along with WPC continuity and the 01 UTC National Blend of Models valid Monday. The larger scale upper flow pattern evolution remains generally compatible in guidance well into medium range time scales and offers some common trend for a slower southern stream solution in recent guidance including the latest 00 UTC runs. However, embedded system timing/surface feature focus and run to run continuity issues build in a sensitive pattern with uncertain multi-stream system interactions. The 12 UTC ECMWF ensembles were not available for this forecast package due to a technical issue, but the 12 UTC NAEFS mean that includes input from both GEFS and Canadian ensembles does seem to provide a decent forecast basis Tuesday-next Friday with and extending from a general composite of varied model guidance in a pattern with less than stellar continunity with local specifics. Accordingly, felt compelled to only broadly imply threat areas and targeted a blend of NBM QPF with some WPC continuity to soften run to run variance and local focus. ...Pattern overview and Weather/Hazard Highlights... Much of the lower 48 will experience progressive flow aloft to channel between a mean closed low/trough over central Canada and a ridge over the Gulf of Mexico next week. Northern stream shortwave around the Canadian vortex may favor some periods of snow from the Midwest to the Northeast. Guidance has trended towards a positively-tilted upper-level trough persisting over the eastern Pacific and western U.S. with only a gradual eastward drift during the early-mid next week prior to later week ejection into the flow. An upstream ridge should move into the Northwest U.S./western Canada by midweek or so, followed by a shortwave trough approaching the Pacific Northwest around Thursday to renew precipitation into the region. This pattern should promote below normal temperatures over most of the West and north-central states on most days, with rain and mountain snow affecting some parts of the West. The pattern also looks to offer a favorable setup for some heavier rainfall over portions of the east-central U.S. next week as multiple lead moisture sources uncertainly interact with a couple fronts, perhaps with a focus from the Tennessee Valley to the southern Appalachians. A mainly dominant northern stream flow and associated settling of colder air to the north of these fronts may also provide a possibility for an overrunning swath of snow/ice/freezing rain on the north side of the rain shields, perhaps from the south-central Plains through the Ohio Valley states mid-later next week. 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