Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 AM EST Wed Jan 16 2019 Valid 12Z Sat Jan 19 2019 - 12Z Wed Jan 23 2019 ...Major Central to Northeastern U.S. Arctic Blast/Winter Storm... ...Guidance Evaluation/Preferences... The WPC medium range product suite was primarily derived from a blend of well clustered guidance from the 12 UTC ECMWF/ECENS and the 18 UTC GEFS. Recent GFS runs are now overall a bit more progressive with systems, albeit with less ensemble support. Despite timing variance, there remains a strong signal for the upcoming major Central to Northeastern U.S. Arctic Blast/Winter Storm. ...Weather Highlights/Hazards... Frigid arctic air spills across the central then eastern U.S. as the northern stream amplifies around a Hudson Bay upper vortex. Underneath, amplified southern stream mid-upper level trough approach/height falls and favorable coupled upper jet support will spawn lead cyclogenesis from the south-central to eastern U.S. over MLK Jr. weekend. Deepening Gulf of Mexico then Atlantic moisture will advect inland in advance and around the developing storm and overrun a sharp arctic front. Heavy snow will spread from portions of the central Plains through the Midwest/Ohio Valley, Appalachians and Mid-Atlantic/Northeast along with some threat of blizzard conditions in the tight pressure gradient between a main surface low and a strong arctic high. Meanwhile, heavy warm-sector rains/strong convection move through the South/Southeast/Mid-Atlantic and a transition zone between snow and rain is likely to include significant sleet and freezing rain. Please consult WPC Day 4-7 QPF and Winter Weather Outlook for a probabilistic assessment of the significant winter weather threat. Upstream, Pacific storm systems will reload with new focus as a heavy precipitation threat into the Pacific Northwest. Wintery weather spreads/moderates inland across the north-central Great Basin/Rockies later in the holiday weekend then across the central U.S. early-mid next week. There is a signal for increased mid-upper level trough amplitude/separation over the s-central U.S., but there is more uncertainty with the specifics of this flow and associated surface system response. However, most guidance supports an increasing lead Gulf moisture inflow and precipitation pattern with additional potential for wintery weather on the cooled northern periphery heading into Tue/Wed. Schichtel WPC medium range 500 mb heights, surface systems, weather grids, quantitative precipitation, winter weather outlook probabilities and heat indexes are found 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