Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1136 AM EDT Sun Jul 22 2018 Valid 12Z Wed Jul 25 2018 - 12Z Sun Jul 29 2018 ...Heavy rain and flooding potential continuing for parts of the East... ...Southwest/West heat wave lasting into mid-late week... ...Central Rockies/Plains to Mid-MS Valley heavy rainfall potential... ...Guidance/Uncertainty Assessment and Weather Threats... Forecast predictability in the medium range period remains much above normal in showing an amplified mid-upper level trough lingering across the East with an axis across the Ohio Valley and into the Deep South. Deep moisture with pooled precipitable water values of 2+ inches feeding into/ahead of the system and associated/slow moving surface fronts/instability will prolong a pattern favorable for cell training/repeat activity. This will continue a threat of locally heavy/excessive rainfall for portions of the Eastern Seaboard. Mid to late week, this system gets replaced by a well defined upstream trough/height falls working across the Great Lakes/Midwest and into the Northeast. This should focus lingering heavy rainfall more into the Northeast/coastal Mid-Atlantic and trailing to FL along and ahead of a cold front. Flash flooding and longer term/larger scale flooding remains possible in the wake of recent heavy rains. Meanwhile, a hot mid-upper level ridge settled over the Southwest and up into the West along with potential for record maximum temperatures will gradually ease through mid-later this week, but monsoonal moisture could allow for more record high minimum temperatures. A series of less predictable impulses rotating within and overtop the ridge interacting with surface convergence boundaries should provide additional lift for heavy convection to develop from the central Rockies/Plains into the Mid-Mississippi Valley. Its here where potential convective complexes/thunderstorms will be fueled by inflow pooling moisture and heavy/repeat cells may lead to a local excessive rainfall threat. Much of this medium range forecast remains of high confidence during this cycle, with strong agreement and clustering among the models and ensembles regarding these well defined and slowly/steadily evolving features. Accordingly, the WPC medium range forecast suite was primarily derived from a majority blend of the latest GFS/ECMWF deterministic runs, with smaller contributions from the GEFS/EC ensemble means. Santorelli/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