Extended Forecast Discussion NWS Weather Prediction Center College Park MD 141 AM EDT Wed Jun 10 2020 Valid 12Z Sat Jun 13 2020 - 12Z Wed Jun 17 2020 ...Overview and Guidance/Predictability Assessment... Upper ridging is forecast to persist over the Southern Plains/southern Rockies northward toward the Corn Belt. This will favor troughing over the Pacific Northwest (and California Saturday) as well as over the East Coast. Through the 12Z/18Z cycle, the models continue to handle the overall pattern adequately, with a few deviations from the good ensemble mean consensus between the GEFS and ECMWF ensembles. In the West, the 12Z Canadian was most unlike the consensus by Sunday (quite deep and far south with the upper low) and preferred the ECMWF/GFS there. Lead front Sat-Mon should fade over the Northern Plains around Tue as another system pushes through WA/OR Mon. In the East, consensus still favors an upper low to split off from the northern stream over Ontario and sink southward along 80W into the central Appalachians. 12Z ECMWF was farther west than about 95% of the ensembles with its track and retrogression in weak flow which is certainly possible but preferred to stay closer to the 12Z GFS/Canadian for now which aligned with the ensemble means. However, the trend across the CONUS has been toward more amplification (and only very transient quasi-zonal flow between western upper lows) which leaves room for the eastern upper low to trend west. ...Weather/Hazard Highlights... Temperatures 10 to 20 degrees above normal will shift out of the High Plains this weekend ahead of the western front into the central Plains with anomalies 5-15 degrees above normal. Behind this system, temperatures will be 5 to 15 degrees cooler than average across the Pacific Northwest and surrounding area this weekend before moderating. Cooler than normal temperatures around the Great Lakes Saturday should shift southeastward to the Mid-Atlantic next week as the front lingers just offshore or even retrogrades back toward the coast. Rainfall should be light over most of the CONUS during the period with the exception over parts of the East Coast. Cold front moving into the Southeast and northern Florida this weekend will focus some rainfall there but will generally by light to modest. With a trend to linger the upper low near the Appalachians next week, rainfall may expand northward along the stalled front just offshore from the Carolinas into the Mid-Atlantic. Details remain tied to the position of the upper and surface features. Over Florida, increased moisture over the northern Caribbean may enhance rainfall next week to southern sections. Front into the Pacific Northwest will bring some light to modest rainfall to especially the higher elevations and some light snow for the highest peaks. The precipitation will spread eastward and diminish a bit as the best dynamics are expected to lift into Canada. Fracasso 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