Extended Forecast Discussion NWS Weather Prediction Center College Park MD 151 AM EDT Mon Jun 22 2020 Valid 12Z Thu Jun 25 2020 - 12Z Mon Jun 29 2020 ...Guidance/Predictability Assessment... Models and ensembles continue to struggle with how to handle troughing exiting the Northwest on Thursday/Day 3. The deterministic ECMWF, as early as day 4, continues to be quite a bit faster with this trough placing the axis on Saturday/Day 5 across the Upper Midwest while the rest of the deterministic guidance holds it back across the Plains, likely due in part to a stronger/more blocky upper low over Hudson Bay. The ensemble means generally follow suit with their deterministic counterparts, albeit rather washed out/flat. Run to run continuity in the deterministic runs though is still all over the place so a blend towards the ensemble means seemed reasonable for now. Opted to incorporate more of the GFS/UKMET which had better support and provided some definition to the ensemble means. By day 6 and 7, this system should weaken in favor of renewed amplified troughing across the West Coast. Normal variability in evolution/strength for this time frame are evident, so a mostly ensemble mean approach was preferred. ...Overview and Weather/Hazard Highlights... A closed upper low held south of Hudson Bay midweek gradually weakens while ejecting over eastern Canada Friday-Sunday. Height falls across the Northeast will drive a cold front off the East Coast on Thursday with showers and thunderstorms likely across parts of the Northeast and the South. Upper level energy combined with the stalled trailing portion of the moisture pooling front supports a period of focused convection from the Southern Plains to the Lower Mississippi Valley. The best chance for heavy rainfall may be near the Texas Gulf Coast region into Thursday. Unsettled weather should continue into the weekend across the South as the trailing boundary lingers and eventually weakens. Meanwhile out West, the next cold front should focus showers and potentially strong thunderstorms from the Northern Plains, into the Upper Midwest, and lower Great Lakes late week into the weekend. Models show the possibility for locally moderate to heavy precipitation, though timing remains in question given model uncertainties. Additional showers and storms may also develop next weekend farther south from the Central Plains/Mid-Mississippi Valley and also across the Northwest as amplified troughing reinforcement settles across the West. This should also help moderate above normal temperatures in the beginning of the period back towards or even below normal by Sunday-Monday. Santorelli 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