Extended Forecast Discussion NWS Weather Prediction Center College Park MD 324 AM EDT Tue Oct 02 2018 Valid 12Z Fri Oct 05 2018 - 12Z Tue Oct 09 2018 ...Stormy Pattern for the West/Rockies and a Central U.S. Excessive Rainfall Threat... ...Pattern Overview and Guidance/Predictability Assessment... Model and ensemble guidance remains well clustered with development of a highly amplified weather pattern for the nation this weekend into next week, strongly bolstering forecast confidence. This pattern offers height anomalies of 2-3 standard deviations above/below normal with a digging western U.S. longwave trough sandwiched between ridges over the eastern Pacific and the East Coast/Atlantic Ocean. A deepening/closed low sets up over the Great Basin region and multiple waves lift from the Great Basin/Southern and Central Rockies into the Plains where a deep layered southerly funnel of Gulf of Mexico moisture pools to 2+ standard deviations from normal into/over a slow moving baroclinic zone. The WPC medium range product suite was primarily derived from a blend of the GFS/ECMWF and GEFS/ECMWF ensemble means that offer a strong signal supporting this threatening pattern. ...Weather Highlights/Threats... Colder than seasonal normal temperatures and highly unsettled/wet weather is expected as a persistent and highly amplified trough mean aloft sets up over the West, especially from the eastern Great Basin/Southwest to the Rockies. Terrain and upslope enhanced snows will spread down over the north-central Rockies and northern Plains, enhanced by a cold high pressure surge early next week. With such a strong warming/blocking ridge over the East, waves along/over the front will show little eastward progression. This will set the stage for a prolonger period favoring multiple rounds of heavy rain/convection with some far northern tier fringe snow. Training offers a widespread excessive rainfall hazard. Temperatures south of the front will be summer-like, so the frontal zone will be stark. Elsewhere, a deep layered easterly fetch off the Atlantic sets up and persists into next week over the Southeast, spreading showers across Florida and the Gulf Coast/northern Gulf of Mexico underneath a northward shifting eastern U.S. closed trough aloft. This leave room for Atlantic energies and a Carribean based tropical disturbance to work into Florida and the Gulf of Mexico next week that may act to enhance lift/moisture pooling. 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