Extended Forecast Discussion NWS Weather Prediction Center College Park MD 113 AM EST Sun Jan 12 2020 Valid 12Z Wed Jan 15 2020 - 12Z Sun Jan 19 2020 ...Weather Pattern/Hazard Highlights and Guidance/Predictability Assessment... Mid-upper level troughing over the West will periodically be reinforced with dynamic eastern Pacific energy, but with a trend toward less amplified flow through later week. Guidance supports a deep low off the Pacific Northwest Wed/Thu that would enhance maritime hazards and inland flow/weather, with energies then working into the West. Details are less certain for upstream storm potential, but a favored guidance composite signal is growing for low development next weekend more off the Pacific Northwest/western Canada. WPC QPFs and winter weather outlook probabilities show a widespread snow threat for the Northwest that reach lower elevations given the extent of cold air filtration. Activity spreads into CA and the north-central Great Basin/Rockies mid-late week. Snows over the northern High Plains/Rockies will be enhanced by post-frontal upslope flow. Activity works back in ernest into the Northwest next weekend. Upper trough energies and surface systems will eject northeastward from the West over the central and eastern U.S. well overtop a lingering and warming/stabilizing Southeast ridge and interacting with a lower atmospheric Arctic airmass. A preferred composite blend of varying GFS/ECMWF and GEFS/ECMWF ensemble guidance highlights a moderately deepening low threat from the central Plains to the Northeast Wed/Thu. The blend is now better clustered with deep cyclogenesis from the Plains to the Midwest/Great lakes to the Northeast Fri-next Sunday, bolstering forecast confidence in this potentially significant system. This would favor heavier rainfall potential later week/next weekend from the south-central U.S. and mid-lower MS/OH Valleys to southern New England. The pattern offers several heavy snow/ice threats in the cooled northern tier from the Midwest/Great Lakes to the northern Mid-Atlantic/Northeast as the deepening frontal lows wrap in deeper moisture as shown by WPC progs, grids, QPFs and winter weather outlook probabilities. 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