Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1057 AM EST Tue Feb 19 2019 Valid 12Z Fri Feb 22 2019 - 12Z Tue Feb 26 2019 ...Multi-day heavy rainfall/flooding threat from the Lower Mississippi/Tennessee/Ohio Valleys to the Southern/Central Appalachians through Saturday... ...Significant snow threat lifts from the Southwest and south-central Rockies states Friday through the Plains/Upper Midwest and Great Lakes/Northeast this weekend... ...Pattern Overview and Weather Highlights/Hazards... A favorable corridor for a multi-day heavy rain/training episode will persist from the lower MS/TN/OH Valleys to the Southern/Central Appalachians and Mid-Atlantic through Saturday. Flooding/runoff issues will be fueled by highly anomalous moisture channeling into a wavy frontal zone under favorable jet support initially, then deeper weekend cyclo/frontogenesis. An amplified upper trough will support terrain enhanced heavy snows over the Southwest and the South-central Rockies states on Friday. The trough lifts through the Central and Northeast U.S. this weekend overtop an amplified and slow to erode Bahamas/Southeast upper ridge. This system will bring a threat for significant accumulating snow with some icing possible with a deepening surface low tracking from the Plains to the Upper Midwest/Great Lakes/New England. Models have come into better agreement compared to previous runs on the strength of the surface low, with most deterministic solutions advertising a surface low by 12z Saturday in the 980s over the Upper Great Lakes. This would likely result in gusty winds and potential blizzard conditions across the Upper Midwest and Great Lakes this weekend. Troughing out west gets reinforced through the medium range period thanks to a blocking ridge situated in the Gulf of Alaska and eastern Pacific. A couple of shortwaves dig southward through the Northwest this weekend/early next week, albeit should be less amplified than the lead systems. This should continue an unsettled weather pattern across the Pacific Northwest and into the Intermountain West, with the best chance for accumulating snowfall in the Washington/Oregon Cascades. ...Guidance/Predictability Assessment and Preferences... Models and ensemble solutions continue to show very good clustering at the mid-larger scales through the medium range period. The morning update to the WPC progs favored a majority blend of the latest runs of the GFS/ECMWF, with smaller contributions from the GEFS/ECMWF ensemble means. This maintains excellent WPC continuity within a pattern with above normal predictability. Santorelli/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