Extended Forecast Discussion NWS Weather Prediction Center College Park MD 154 AM EST Tue Jan 21 2020 Valid 12Z Fri Jan 24 2020 - 12Z Tue Jan 28 2020 ...Overview... A system over the mid-Mississippi Valley/Southeast Friday will lift through the Mid-Atlantic Saturday and near Long Island Saturday. The West will see a continued chorus of Pacific systems that will weaken once inland this weekend but likely trend stronger by next week. Upper troughing is forecast to deepen early next week in the West/Southwest as heights rise in the wake of the Eastern system. ...Guidance/Predictability Assessment... The 12Z ECMWF/Canadian/UKMET formed a close consensus overall for the Fri-Sun period with the GFS weaker in the Pac NW and over Montana Fri/Sat but otherwise close to the other models/ensembles in the East. This general blend sufficed as a starting point until next Monday when the ensembles diverge on the speed and somewhat the depth of western troughing (the Canadian being flatter and quicker), but at least agree that heights should fall over the Great Basin/Rockies and rise in the East. Ensemble means, especially the ECMWF ensemble mean, have been fairly consistent in timing/depth but still show spread mostly to the east and west, suggesting timing rather than depth would be the larger discrepancy. Used a majority ensemble weighting by the end of the period to mitigate future deterministic changes. ...Weather/Hazard Highlights... Above average temperatures are favored nearly CONUS-wide through the period. The highest anomalies of 10-25F above average will be focused over the northern tier (High Plains and Upper Midwest/western Great Lakes) with lower anomalies both east and west. Near average or a bit below average temperatures (especially max temperatures) will follow along the path of the southern/eastern system. Intermittent periods of precipitation can be expected across the Northwest and parts of California and the Interior as several systems make their way through the region. Snow levels will be near or above average given the overall milder pattern. To the east, rainfall will expand out of the lower Mississippi Valley to points eastward/northeastward as the system lifts across the Tennessee Valley. Modest to locally heavy rainfall is possible over the southern Appalachians and maybe into the Mid-Atlantic. Snow is likely on the northern side of the precipitation shield in marginally cold air (away from the coast). Higher elevations of the central Appalachians are favored to see some snowfall with higher chances extending across the Endless Mountains of northeastern Pennsylvania and Poconos, then into the Catskills and Berkshires, and finally into the Green/White mountains and Maine. Fracasso 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