Extended Forecast Discussion NWS Weather Prediction Center College Park MD 245 AM EDT Mon Oct 01 2018 Valid 12Z Thu Oct 04 2018 - 12Z Mon Oct 08 2018 ...A Wet Pattern for the West/Rockies and a Central U.S. Heavy Rainfall Threat... ...Pattern Overview and Guidance/Predictability Assessment... The WPC medium range product suite was primarily derived from a blend of the GFS/ECMWF and GEFS/ECMWF ensemble means. These guidance solutions remain well clustered, bolstering forecast confidence. Flow amplification makes sense considering the amplified upstream Pacific/Alaskan flow enhanced in part with entrainment of western Pacific tropical lows. ...Weather Highlights/Threats... Persistent and highly amplified troughing aloft over the West will be reinforced from the northeast Pacific and western Canada that acts to keep colder than normal temperatures and unsettled/wet weather for much of the west and into the Plains to the north of a wavy surface front with post-frontal Canadian high pressures surges. This will include terrain and upslope enhanced snows over the northern Rockies/Plains. With the upper ridge in the east/southeast anchored in place, the front will be prevented from moving much to the southeast as waves of low pressure (including the remnants of Rosa) lift along a similar path from the central Plains to the Great Lakes. This will bring rounds of rain (and some northern fringe snow) to the same areas over several days giving way to wetter soils and rising rivers. Temperatures to the south of the front will be rather summer-like into the 80s and some 90s along the Gulf Coast. By the coming weekend, additional troughing into the west will nudge the trough axis eastward into the Great Basin with more rain and high mountain snow into the north-central Rockies and an emerging heavy rainfall and strong convection threat spread down into the southern Plains with mid-level southwest flow atop the lingering surface front. This will promote a prolonged pattern that offers a risk of cell training within an increasingly deep moisture channel east of the western U.S. mean trough and around the amplified ridge holding in place over the East/Southeastern U.S. Schichtel WPC medium range 500 mb heights, surface systems, weather grids, quantitative precipitation, winter weather outlook probabilities and heat indexes 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 https://www.wpc.ncep.noaa.gov/heat_index.shtml