Extended Forecast Discussion NWS Weather Prediction Center College Park MD 147 AM EST Mon Feb 17 2020 Valid 12Z Thu Feb 20 2020 - 12Z Mon Feb 24 2020 ...Guidance/Predictability Assessment... Recent model and ensemble forecast spread remains below normal for the rest of this week, increasing early next week. However, lingering system timing and emphasis differences seem well mitigated by the blending of overall reasonably well clustered guidance through medium range time scales. The WPC medium range product suite was based primarily from a composite blend of the 18 UTC GFS/GEFS mean, 12 UTC ECMWF/UKMET/Canadian/ECMWF ensemble mean and the National Blend of Models. Opted to marginally trend WPC blend weighting from the models toward the ensemble means into days 6/7 consistent with growing solution variance within the full envelope of solutions. This strategy maintained good WPC continuity. The latest 00 UTC GFS/GEFS/ECMWF/UKMET generally seem in line with this WPC forecast. ...Weather Pattern and Hazard Highlights... Cold post-frontal high pressure will settle over much of the lower 48. A positive tilt northern stream mid-upper level trough and limited/spotty snow will progress from the Midwest to off the East Coast Thu/Fri in response to deamplification of upstream ridging aloft over west-central Canada. More organized precipitation lingering from the southern Rockies to the South/Southeast U.S. within a trailing and wavy cold frontal zone will gradually be suppressed across the region. Meanwhile, an amplified upper trough/low will develop in emerging and separating southern stream flow off the West Coast. Dynamics/height falls with inland trough progression and cyclogensis/frontogenesis should support moderately increasing precipitation to spread this weekend from the Southwest to the south-central U.S. Activity may increase over the mid-lower MS/TN Valleys through the South/southern Appalachians into Mon as fueled by increasingly favorable Gulf of Mexico return moisture into a region with ongong runoff issues. There is also some potential for snow/ice on the cooled northern periphery of the precipitation shield. Upstream, development and weekend approach of an amplified upper level trough and surface front may support potential for increasingly wet flow into the Pacific Northwest Sun. Unsettling sharp system digging over the West Mon would deliver cold air and a terrain focusing snow risk down through the Great Basin/Rockies. 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