Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1100 AM EST Sun Feb 03 2019 Valid 12Z Wed Feb 06 2019 - 12Z Sun Feb 10 2019 ...Overview... Positive height anomaly near the Gulf of Alaska will favor western CONUS troughing Wed-Sun and broad SW upper flow in the eastern states. Subtropical upper high will drift out of the Bay of Campeche and into the Florida Straits which will largely keep the storm track through the Midest/Great Lakes and St. Lawrence Valley. ...Guidance/Predictability Assessment and Preferences... Alaskan and Pacific upstream flow and northern/southern stream separation over the West continues to be poorly resolved by the models/ensembles with noticeable run-to-run changes. The ECMWF and its ensembles have been quite different than the GFS and to a lesser extent GEFS ensembles, while the Canadian and its ensembles mostly clustered near the ECMWF ensembles. Recent GFS runs in particular seem quite the outlier upstream over the northeast Pacific and Alaska in breaking energy more readily through the ambient longwave mid-upper level ridge position. Prefer the cluster near the ECMWF ensemble mean which showed a bit quicker exit of a main trough out of the Rockies late Wed/early Thu. This maintains good WPC continuity. Weather Highlights/Hazards... Above average temperatures in the Southeast/East (with record highs possible) will be replaced by nearer to average temperatures as the cold front clears the East Coast, but not through Florida thanks to the strong upper ridge. In the northern tier from MT to the Upper Midwest, temperatures will remain well below average behind an arctic front that will get hung up near the Divide (but still bring cold air to the Pacific Northwest via northern stream height falls). Storm track favors snow and low elevation rains that exit the Rockies midweek and additional but uncertain influx of shortwave impulses will keep upstream flow into the west wintry and unsettled. Downstream, a swath of heavier precipitation will spread across the Plains through the OH Valley and into the northern Mid-Atlantic/Northeast. This will include a significant heavy snow/ice threat around the north/northwest side of developing surface lows in the arctic airmass. Frontal/warm-sector rains may be locally heavy from the mid-MS Valley through the OH Valley states and northern mid-Atlantic, but trend lighter to the south under stronger upper ridging and weaker dynamics. As the main low pulls away, lake-effect snow will resume at least Friday into Saturday. Fracasso/Schichtel WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation and winter weather outlook probabilities 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