Extended Forecast Discussion NWS Weather Prediction Center College Park MD 312 AM EDT Sun Oct 23 2022 Valid 12Z Wed Oct 26 2022 - 12Z Sun Oct 30 2022 ...Guidance and Predictability Assessment... Model and ensemble solutions continue to trend towards better agreement, bolstering forecast confidence longer into medium range time scales. The WPC product suite was mainly derived from a blend of the best clustered model guidance from the 18 UTC GFS and 12 UTC ECMWF/UKMET Wednesday-Friday, along with input from the compatible 01 UTC National Blend of Models (NBM). Latest 00 UTC guidance remains in line and this soluiton seems supported by GEFS/ECMWF ensemble means and WPC product continuity. Opted to compose a longer range solution closest to the 12 UTC GEFS mean and especially the more stream separated 12 UTC ECMWF ensemble mean next weekend given growing uncertainties. Ensemble mean usage was part of an effort to mitigate growing individual system timing and strength differences at these longer time frames, but injection of some input from the 12 UTC GFS/ECMWF added in particular more system definition and weather focus consistent with ongoing separated stream flow history. The main targeted change to 01 UTC NBM QPF across the forecast domain and time scales was to lessen NBM run to run continuity variance by incorporating some WPC product continuity. ...Pattern Overview and Weather/Hazard Highlights... A dynamic upper trough/closed low will lift/shear northeastward from the Midwest to eastern Canada Wednesday into Thursday. Timing and amplitude issues remain in the guidance, but forecast spread has steadily decreased over the past few days to afford a blended GFS/ECMWF/UKMET model foreast approach. Recent Canadian runs have seemed a bit too quick to lift the system north given initial closed system nature. The pattern may focus some Gulf of Mexico and Atlantic moisture into the leading frontal system across a broad region, but progression should mostly favor an increasingly more scattered precipitation patttern, albeit with some Great Lake enhancement possible after the upper low moves through. Ample midweek upper trough energy into the West Coast and subsequent southern stream flow amplification inland across the Interior to the Rockies sets the stage for some much below normal cold temperatures and a moderate QPF coverage response to include terrain enhanced heavy snow threats from the Great Basin to the Rockies Wednesday into especially Thursday. Additional flow/digging of upstream Pacific system/upper energies into the West become too chaotic in the models to offer sure focus, but the less defined ensemble means at least show potential energy available along with a modest model, ensemble and NBM QPF signature back across mainly the Northwest and inland into the north-central Great Basin and Rockies. Meawhile, the downtream ejection of a main and possibly closed/well separated southern stream system in this active pattern remains slated to again mainly emerge over the south-central to southern U.S. late next week into next weekend to renew rain/convection, although uncertainty on placement/amounts remain highly variable, suggesting prudence with rainfall amounts at this juncture despite higher potential. 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