Extended Forecast Discussion NWS Weather Prediction Center College Park MD 225 AM EDT Sun Jul 25 2021 Valid 12Z Wed Jul 28 2021 - 12Z Sun Aug 01 2021 ...Overview with Weather Highlights/Hazards... Models and ensembles consolidate a closed upper high down over the central Plains mid-later this week, with ridging spreading back to the north-central Intermountain West. The best chance for record high maximum/minimum temperatures may be over the Great Plains midweek, but record high minimum temperatures will occur across the Great Basin/Rockies into late week and eventually the West Coast by the weekend as moisture lifts across the region between the ridge/closed high and amplifying eastern Pacific troughing. Expect increasing chances for monsoonal rainfall will extend from the Southwest/California to the Great Basin and Rockies. Meanwhile, multiple shortwaves will dig downstream from the ridge to amplify a mean upper trough over the Midwest/Northeast. Strong convection and locally heavy downpours may periodically focus with moisture/instability pooling near wavy and slow moving fronts and meso-boundaries under favorable upper support. Frontal progression should shift best focused rainfall chances from the Midwest/Great Lakes through the northern Mid-Atlantic midweek to from the Mid-South through the Carolinas by the weekend. Underneath, the National Hurricane Center continues to monitor potential for short range tropical cyclone formation east of northern Florida. The disturbance may intensify and drift inland to the Gulf Coast midweek with deepened moisture to fuel local downpours. ...Guidance/Predictability Evaluation... The medium range pattern evolution at mid-larger scales overall seems to offer slightly above average predictability Days 3-7. However, the least certain mass field part of the forecast remains across the Midwest/Northeast where models continue to struggle with resolving the various shortwave interactions within a mean trough position. A variety of solutions unfold over time with regards to the timing and intensity of shortwaves withing the upper trough and surface low pressure system developments. However, an overall trend in guidance over the last few days to develop an unseasonably amplified upper trough seems reasonable considering the strength of the upstream ridge. Accordingly, the WPC medium range product suite was primarily derived from composite blend of the latest GFS/ECMWF/UKMET/Canadian along with the National Blend of Models for days 3/4 (Wed/Thu) before focusing more on GEFS/ECMWF ensemble means days 5-7 amid growing forecast spread with flow embedded features. 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