Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1200 PM EDT Wed May 15 2019 Valid 12Z Sat May 18 2019 - 12Z Wed May 22 2019 ...Guidance/Predictability Assessment... The 06 UTC GFS/FV3 and 00 UTC ECMWF/UKMET/Canadian offer good forecast clustering this weekend. Despite some common longer term model similarities, forecast confidence next week remains below normal due to less than stellar continuity issues. Accordingly, the WPC product suite primarily was derived from a composite model solution this weekend before quickly transitioning to more compatable 06 UTC GEFS mean and 00 UTC ECMWF ensemble mean into early next week amid growing forecast spread....Guidance Assessment and Weather Highlights/Threats... ...Weather Highlights and Hazards... Model and ensemble solutions continue to show above normal forecast spread with respect to northeastern U.S./Mid-Atlantic flow through this weekend as a series of potent Canadian upper systems progress within an energetic northern stream. Favor a composite. Upstream, a dynamic mid-upper level trough will lift northeastward from the southern Rockies to the central then northeastern U.S. Sat-Tue. This system will spawn surface system/low genesis with lead moisture inflow and instability providing the foundation for a threat of heavy convection/rainfall and severe weather as per SPC. Underneath, a gradually weakening closed low/convection will weaken over the eastern Gulf of Mexico. There remains a strong signal that Pacific flow will bring another round of strong height falls and widespread precipitation/terrain enhanced snows to the West later this weekend into early-mid next week before ejecting over the central U.S. Further upstream, there is a still uncertain guidance signal to develop a deeper low in the eastern Pacific early next week that offers potential to reach CA and the Great Basin/Southwest again early next week along with renewed unsettled weather/precipitation. 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