Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1252 AM EST Mon Feb 18 2019 Valid 12Z Thu Feb 21 2019 - 12Z Mon Feb 25 2019 ...Multi-day heavy rain event from the Lower Mississippi/Tennessee Valleys to Southern/Central Appalachians... ...Wintry heavy precipitation threat for the Southwest and south-central Great Basin/Rockies Thu into Fri... ...Pattern Overview and Weather Highlights/Hazards... What has proven to be quite the persistent and wintry western U.S. mean upper trough will again be reinforced into Thu-Fri, spreading an enhanced precipitation threat to include higher elevation heavy snows from srn CA to the s-central Great Basin/Rockies. Trough energy ejects over the central then eastern U.S. over the weekend, working overtop an amplified and slow to erode Bahamas upper ridge. A favorable corridor for a multi-day heavy rain/training episode persists from the lower MS/TN/OH Valleys to the Srn/Central Appalachians and Mid-Atlantic. Flooding/runoff issues will be fueled by highly anomalous moisture channeling into a wavy frontal zone under favorable jet support. A threat for heavy snow/ice develops from the n-central Plains to the Midwest/Great Lakes/Northeast as enhanced by less certain but potentially deep surface cyclogenesis Fri-Mon. Upstream, weaker trough energies dig into a less unsettled West in transition to less stormy and moderating lower 48 mean zonal flow. ...Guidance/Predictability Assessment and Preferences... Models and ensembles overall cluster pretty well into Thu/Fri with the larger scale flow evolution and a favored composite solution of the GFS/ECMWF and GEFS/ECMWF ensemble means maintains good WPC continuity in a pattern with above normal predictability. Recent ample run to run model variance prompts a quick transition in favor of these ensemble means over the weekend into early next week amid growing uncertainty in transitional flow. 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