570 FXUS02 KWBC 250607 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 207 AM EDT Mon Mar 25 2019 Valid 12Z Thu Mar 28 2019 - 12Z Mon Apr 01 2019 ...Overview... A potent/closed eastern Pacific upper trough will approach the West Coast midweek, with these southern stream height falls working eastward over the nation Thu-Sun. Surface fronts in the West will support some heavy precipitation including heavy elevation snows. Low developments in the Plains and subsequent movement through the MS Valley/Midwest will combine with a surge of deepening moisture/warmth from the Gulf of Mexico, which may fuel enhanced rain/thunderstorms in those areas late week into the weekend. The fronts/waves and moderating precipitation will mainly exit the East Sun. This pattern also includes a risk of heavy snows Thu-Sun on the cooled northwest to northern periphery of the precipitation shield from the n-central Rockies/Plains to the Midwest/Great Lakes and northern New England. ...Guidance Assessment/Preferences... A multi-model blend seems quite reasonable Thu into Sat for the larger-scale features (upper trough/low entering the West with some downstream ridging all underneath a east-central Canadian upper trough) while de-emphasizing the small-scale differences. This blend includes the latest GFS, ECMWF, and UKMET that cluster well with the latest GEFS/ECMWF ensemble mean during this time period. Forecast spread and model run to run continuity issues become more problematic over the weekend and next Mon. Accordingly preferred a blend of the more compatable GEFS/ECMWF ensemble means, with more weight assigned to the ECMWF ensembles that maintain somewhat better 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 expected into Thu. Some heavier valley rain/mountain snows will threaten northern California/Oregon through the Northern Rockies, with heavy snow forecast for the Central Rockies by Thu/Fri. As the trough energy ejects out through the West, it is expected to induce cyclo/frontogenesis in the Plains then Mississippi Valley, Midwest and Northeast. This plus a northern stream cold front dropping southward out of Canada will work in tandem with deepening lead return flow from the Gulf of Mexico to fuel an expanding risk of enhanced rains/convection. In the cold air behind the aforementioned cold front coming from Canada, late-season snow is possible in the Northern/Central Plains to Midwest/Great Lakes then northern New England. 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 $$