Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1159 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. Northern stream flow will feature a persistent upper ridge over central Canada with a couple of frontal waves moving across the central U.S. The first wave is forecast to lift across the Midwest into the Great Lakes late this week into the weekend while a second wave digs across the northern Rockies during the weekend and moves into the northern Plains early next week. Both the GFS and ECMWF solutions and ensembles agree very well with this general scenario, although the GFS shows a more amplified solution with the second trough over the Rockies coupled with a stronger ridge over central Canada. Over New England, the Canadian model indicates the formation of a nor'easter early next week but this is not supported by its own ensemble mean nor the GFS and ECMWF solutions. Therefore, the WPC medium range product suite was primarily derived from a composite blend of well-clustered model guidance from GFS/ECMWF with limited ensemble input. ...Weather Highlights/Threats... Precipitation should be focused along the mean storm track from the northern Rockies into the central Plains toward the Midwest and the Great Lakes through early next week. The dynamics appear to be not strong enough to result in widespread excessive rainfall. Nevertheless, locally heavy rains associated with convective complexes are possible, with the best chance across the central Plains. Elsewhere, heat is expected to build eastward from the Desert Southwest into western Texas this weekend. No significant tropical systems are expected to impact the U.S. through early next week. Kong 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