Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Sun Mar 24 2019 Valid 12Z Wed Mar 27 2019 - 12Z Sun Mar 31 2019 ...Overview... A closed eastern Pacific upper trough will reach the West midweek, with height falls working eastward over the nation Thu-next Sun. Surface fronts in the West will support some heavy precipitation including heavy elevation snows, and low developments in the Plains and subsequent movement through the MS Valley/Midwest may combine with a surge of deepening moisture/warmth from the Gulf of Mexico to fuel some enhanced rain/thunderstorms in those areas later week. The pattern also includes a risk of wrap-around post-frontal snows on the cooled northwest periphery of the main precipitation shield. ...Guidance Assessment/Preferences... A multi-model blend has been working well into day 3/4 for the large-scale features while de-emphasizing the small-scale differences in the forecast models were in general agreement for the upper low in the eastern Pacific moving eastward into the CONUS. Prefer an ensemble mean forecast approach days 5-7 in a period of growing forecast spread, leaning more on ECMWF ensemble mean to maintain max WPC continuity. ...Weather Highlights and Hazards... With the upper trough/low approaching the West, a couple of fronts will make their way through the West and some heavy precipitation is expected Wed/Thu. Heavy valley rain/mountain snows will threaten northern California/Oregon through the northern Rockies, with heavy snow forecast for the Central Rockies into later week. As the trough energy ejects out through the West, it is expected to induce cyclo/frontogenesis in the Plains. This plus another cold front dropping southward out of Canada in tandom with deepening lead return flow from the Gulf of Mexico would fuel an expanding risk of enhancing rains/convection. The emerging heavy rain area threatens areas of the Mississippi Valley/Midwest (where flooding is ongoing) heading into next weekend. Uncertainty remains regarding heaviest rainfall amounts/placement, but the guidance signal for development continues to grow. In the cold air behind the aforementioned cold front coming from Canada, late-season snow is possible in the Northern/Central Plains to Midwest. 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