Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Thu Sep 19 2019 Valid 12Z Sun Sep 22 2019 - 12Z Thu Sep 26 2019 ...Imelda moisture to fuel Mid-MS Valley/Midwest to Northeast Heavy Rains Sun/Mon... ...Overview and Guidance Evaluation/Preferences... Models and ensembles continue to mainly offer a reasonably similar medium range flow evolution in a pattern with above average forecast confidence. The WPC medium range product suite was primarily derived from a composite blend of fairly well clustered guidance from the GFS/ECMWF/UKMET/Canadian, GEFS/ECMWF ensemble means and the National Blend of Models into early next week. Adjusted the blend to a combination of the better clustered solutions of the ECMWF and GEFS/ECMWF ensembles by next midweek. ...Weather Highlights/Threats... Deep tropical moisture with the remains of Imelda will fuel a threat of locally excessive rainfall. Entrainment into mid-latitude flow ahead of an approaching upper trough and surface frontal system will focus moisture/heavy convective storm potential with cell training/heavy downpours from the Mid-MS Valley to the Great Lakes/Northeast. This occurs as the amplified upper trough ejects northeastward over the Plains this weekend, then eastward over the Midwest/Great Lakes/Northeast early next week. Upstream, upper low/trough energies and precipitation potential will reload back into an unsettling West Coast Sun/Mon. The risk then shifts to the Southwest where moisture from Lorena is drawn into AZ/NM as the low cuts off near CA. The combination of monsoonal/tropical moisture will lead to a heavy rain threat through midweek. Schichtel Additional 3-7 Day Hazards information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, 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/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml