Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Tue Jun 19 2018 Valid 12Z Fri Jun 22 2018 - 12Z Tue Jun 26 2018 ...Guidance/Predictability Assessment... Models show above normal agreement with the flow pattern evolution during the medium range, bolstering forecast confidence. Nrn stream flow will feature a persistent upper ridge over central Canada sandwiched by early next week by amplified wrn Canada/nwrn U.S. and ern Canada/nern U.S. cooling troughs. A modestly progressive pattern underneath across the CONUS has some tendency for system amplification. Energy crossing from the Rockies to the central U.S. offers potential for deepening and/or closing off, moving through a region of relatively weak upper flow beneath the Canadian ridge before being forced downstream. The WPC medium range product suite was primarily derived from a composite blend of reasonably well clustered model guidance from GFS/ECMWF, the National Blend of Models, and WPC continuity, with limited ensemble input. ...Weather Highlights/Threats... Lead mid-Mississippi Valley closed trough/low energy Friday shears northeastward through the Ohio Valley and Northeast over the weekend, and the trailing front sinks down across the ern U.S. This occurs as an amplifying upstream kicker shortwave trough digs from the nwrn U.S. southeastward over the Rockies to the north-central states. Guidance with these systems produce a well developed series of surface lows along a main frontal boundary from the Plains to the MS/OH valleys and mid-Atlantic/Northeast. Expect repeat periods of locally excessive convective complexes/rains to focus along this boundary and into the warm sector aided by tropical moisture influx from the Gulf of Mexico. A late season cooling front next weeks show promise to work into the nwrn us. Schichtel WPC medium range forecasts of 500 mb heights, surface systems, weather grids, quantitative precipitation, and winter weather outlook probabilities are found at: http://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif http://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif http://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html http://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml http://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4