Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 AM EST Fri Jan 10 2020 Valid 12Z Mon Jan 13 2020 - 12Z Fri Jan 17 2020 ...Weather Pattern/Hazard Highlights and Guidance/Predictability Assessment... A closed low/trough will shift from the Canadian Rockies eastward across southern Canada to the Canadian Maritimes Monday-next Friday and a cold arctic airmass coincident with lower atmospheric high pressure will spill southward through the Northwest and the central and eastern U.S. in the wake of passage. This offers a threat for a swaths of snow across the U.S. northern tier of the central and eastern U.S., albeit with mainly modest QPF. Meanwhile underneath, an amplified mid-upper level mean trough will periodically be reinforced with eastern Pacific energies that dig over an unsettled western U.S. next week. WPC winter weather outlook probabilities show a widespread snow threat over the Northwest that may work down to lower elevations given the extent of cold air filtration. Activity will spread down into the Sierra and out across the north-central Great Basin/Rockies with system progressions. Trough energies and associated surface systems will tend to eject east-northeastward out from the West over the central and eastern U.S. overtop a lingering and warming/stabilizing Florida mean ridge. There remains much uncertainty with potential cyclogenesis scenarios in advance of the northern stream cold surge and along lead fronts, but the pattern seems to favor the heaviest rainfall potential next week from the lower MS Valley and Mid-South through the Southeast overtop the shielding Florida ridge. The latest models and ensembles are tending to converge upon a more common solution with mid-scale systems embedded within complex and progressive flow over the lower 48 states. This bolsters forecast confidence a bit, but recent runs of the ECMWF have been erratic and still offer more variance than desired. Accordingly, the WPC medium range product suite was primarily derived from a composite blend of the more compatable and run to run stable 18 UTC GFS and 12 UTC ECMWF ensemble mean along with the 00 UTC National Blend of Models. This blend maintains good WPC forecast continuity. 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