Extended Forecast Discussion NWS Weather Prediction Center College Park MD 248 AM EDT Fri Jul 23 2021 Valid 12Z Mon Jul 26 2021 - 12Z Fri Jul 30 2021 ...Heatwave with some Record Temperatures for the North-Central U.S... ...Overview with Weather Highlights/Hazards... Hot upper ridging will consolidate and strengthen over the north-central Rockies/Plains next week. The heatwave offers some records/triple digit temperatures. Flow over the ridge will feed into a Great Lakes/Northeast mean trough aloft. Moisture and instability pooling along a wavy frontal zone and upper difluence/jet will intermittently fuel scattered heavy convection and downpours out from the Northern Plains, Midwest and the Northeast through the Mid-Atlantic. Meanwhile, an upper low drifting offshore into the Pacific and the strengthening/consolidation of the Rockies-Plains upper ridge next week should act to spread moisture to the north and west out from from the Southwest. Activity to extend into California, the Great Basin, and northward over the Rockies should be less intense than a mainly short term focusing Arizona event. Guidance also suggests that a surface trough with one or more embedded lows off the Southeast coast lingering into early-mid next week offer modest development potential. NHC will monitor. ...Guidance/Predictability Evaluation... The WPC medium range product suite was primarily derived from best clustered guidance from the 18 UTC GFS and 12 UTC ECMWF/UKMET days 3-5 (Mon-Wed) along with 01 UTC National Blend of Models. The ECMWF seems to remain the best clustered model with the GEFS/ECMWF ensemble means into days 6/7 in a period of gradually growing forecast spread, but still above normal average predictability beyond smaller scales. 00 UTC models remain in line with the most variance still with periodic energy amplitude feeding into the Great Lakes/Northeast upper trough. Schichtel Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook 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