Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1211 AM EDT Thu Jul 26 2018 Valid 12Z Sun Jul 29 2018 - 12Z Thu Aug 02 2018 ...Heat wave lingers over the West... ...Heavy rainfall threat to spread from the Central Plains to Mid-South then the Southeast/Eastern U.S... ...Pattern Overview and Weather Highlights/Threats... Potent mid-upper level ridges center over the Southwest and western Atlantic, with the latter retrograding back toward the Gulf Stream. Sandwiched in between this pair of 2 sigma positive height anomalies will be another wet cut-off low meandering about the Mid-MS Valley/mid-South early to mid next week. Otherwise, a weak longwave trough offshore the Pacific Northwest early next week gradually ejects inland to moderate flow. Active impulses linger in the Southwest/srn Rockies and over the ridge. These dig into the central U.S. in favorable upper diffluence to interact with surface boundaries, instability, and favorable low level moisture inflow/convergence. Weekend mid-upper level trough amplification over the n-central U.S. will dig through the MS Valley early next week and induce frontal lows and gradual fronal system progressions downstream over the E-Central U.S. Expect multiple episodes of heavy convection from the central Rockies/Plains through the mid-lower MS/Mid-South this weekend whose threat spreads over much of the E-Central to Southeast/ern U.S. next week. Heavy rainfall with repeat cells offer a widespread excessive rainfall threat fueled by an increasingly deep layered moisture inflow pattern to align roughly parallel to the main front as storms channel between the slow to translate upstream trough aloft and a downstream western Atlantic ridge. ...Guidance/Uncertainty Assessment... The WPC medium range product suite was mainly derived from a composite blend of the 12 UTC ECMWF and 18 UTC GEFS/12 UTC ECMWF ensembles in a pattern with average to below normal forecast spread/uncertainty. The ECMWF is on the amplified side of the full envelope of solutions and that trend seems reasonable given overall anomalous flow characteristics and recent flow history. This solution maintains very nice WPC continuity. 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