Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Wed Oct 11 2023 Valid 12Z Sat Oct 14 2023 - 12Z Wed Oct 18 2023 ...Excessive rain threat focus to the northern Mid-Atlantic Saturday... ...Guidance Evaluation/Predictability Assessment... Model and ensemble forecast spread remains below average through the weekend into Monday in a pattern with seemingly better than average predictability for flow evolution and main embedded weather focusing storms/systems. The WPC product suite was primarily derived from a composite blend of best clustered guidance in this period of the 12 UTC ECMWF/Canadian/UKMET and GEFS/ECMWF ensemble means along with the compatible 01 UTC National Blend of Models. Shifted to the ensemble means at longer time frames amid growing but reasonably manageable forecast spread/uncertainty in a pattern with more average predictability. WPC product continuity is well maintained with this forecast plan. A composite of latest 00 UTC guidance seems overall in line with this forecast scenario. ...Weather/Hazards Highlights... A dynamic upper trough/closed low and deepened surface low/frontal system still slated to steadily track from the Midwest/Great Lakes through the northern Mid-Atlantic/Northeast this weekend to then reform as a coastal storm and maritime threat. This will spread heavy rains through the northern Mid-Atlantic and southern tier of the Northeast as moisture inflow is sustained with deep influx from the Atlantic. The WPC Day 4/Saturday Excessive Rainfall Outlook depicts a "Marginal Risk" area for this region. Expect enhanced winds far around this multi-phased system. Energies will also then continue to dig into an amplifying/unsettling eastern continent upper trough position early-mid next week to the lee of amplified/warming upper ridging from the Intermountain West to the Canadian Prairies. Meanwhile upstream, a complex series of systems will act to amplify an eastern Pacific upper trough position and also bring moisture inland to fuel moderate to heavy precipitation for the Northwest, but particularly favored terrain of the Pacific Northwest in a wet period late weekend/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 forecast, excessive rainfall outlook, winter weather outlook probabilities, heat indices and Key Messages 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 https://www.wpc.ncep.noaa.gov/#page=ovw