Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1200 PM EST Sat Feb 15 2020 Valid 12Z Tue Feb 18 2020 - 12Z Sat Feb 22 2020 ...Guidance/Predictability Assessment... Model and ensemble spread has decreased significantly compared to the past several days, bolstering forecast confidence through medium range time scales. The forecast was updated to incorporate a selection of the latest guidance, including a 00Z ECMWF/06Z GFS blend during days 3-5 (Tue-Thu), and a trend toward increased ECENS/GEFS ensemble mean weighting during days 6-7 (Fri-Sat). Overall, models continue to show relatively good consistency with respect to the most significant features affecting the CONUS during the medium range. Resultant changes to the ongoing forecast were relatively minor. ...Weather Pattern and Hazard Highlights... Impulses digging to the lee of an amplified northeast Pacific/northwest Canadian upper ridge early next week will reinforce a west-central U.S. upper trough. Expect a periodic threat of terrain enhanced snows for the Great Basin/Rockies. Lingering troughing aloft may allow modest activity persist into mid-later week. Trough/jet energies aloft progress downstream to support downstream development of an organized frontal wave into the Great Lakes Tue then Canadian Maritimes Wed. Expect an emerging threat of warm sector rains/convection Tue into Wed, especially over the wettened southern Appalachians/Southeast as Gulf of Mexico moisture feeds inland. There is meanwhile a risk for enhanced snow/ice as moisture and warm air advect over receding dammed cold surface high pressure over the Northeast and with wrapback flow/lake effect back into the Great Lakes. Post-frontal high pressure/cold air will dig over much of the lower 48. A wintry precipitation focus may remain over a trailing frontal zone back across the southern U.S. tier including the southern Appalachians into later next week and especially the cold southern High Plains in upslope flow as additional impulses progress over the region. Ryan/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