Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Tue Oct 25 2022 Valid 12Z Fri Oct 28 2022 - 12Z Tue Nov 01 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 Friday along with compatible input from the 01 UTC National Blend of Models (NBM) and WPC continuity. Latest 00 UTC model and ensemble guidance still seems in line with this early period forecast in a pattern with seemingly above normal predictability. Forecast spread grows steadily through the weekend into early next week. A solution closest to the ECMWF ensemble mean is preferred in this period with lowering predictability as it steadily remains most in line with overall Pacific system translations into the West and downstream southern stream flow separation and embedded system strength/timing aspects compared to WPC continuity as well as the composite of increasing varied over time GFS/ECMWF/UKMET/Canadian models. ...Pattern Overview and Weather/Hazard Highlights... The aspects of a series of Pacific systems into the West/Northwest heading into this weekend and through early next week remains uncertain and more run to run varied than normal in recent guidance, but a general model consensus/ECMWF ensemble mean suggests a system focus for periodic moderate precipitation from northern California and the Pacific Northwest inland across the northern Great Basin/Rockies to include terrain enhanced elevation snows. Latest guidance including the 00 UTC model suite shows a steady diet of systems, but with the strongest system passage/height fall focus seemingly on tap for Sunday into Monday. Overall, 01 UTC NBM QPF seems broadly reasonable with this scenario, continuity and messaging, so targeted changes were not applied. Meanwhile, a leading closed/separated southern stream system remains slated to slowly track across the south-central U.S. Friday and for the weekend before lifting/shearing northeastward toward the Appalachians by next Tuesday. This will act to focus some enhanced rain/convection given upper and surface system support to pool moisture/instability to fuel activity. There is a some guidance signal for locally moderate to heavy rainfall given the risk of repeat/training cells with overall slow system translation, albeit with details less certain given the nature of closed features. Guidance shows the greatest consensus on the potential for higher rain rates and more than a couple inches of rain on Friday, which despite overall dry antecedent conditions, could be enough to lead to at least a few local instances of flash flooding. This often happens with closed systems. Weekend to early next week rainfall from the South northeastward into the East were adjusted slower and accordingly increased relative to the NBM along the track of the system considering trends from deterministic guidance and the ECMWF ensemble mean. However, as expected compared to earlier in the period, the location of any enhanced rainfall is more uncertain and a broad areal average increase was included for now. 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