Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Sun Jun 20 2021 Valid 12Z Wed Jun 23 2021 - 12Z Sun Jun 27 2021 ...Heat intensifies late week over the interior Northwest/West toward record levels... ...Mid-late week heat for portions of the Plains... ...Overview... Ample upper ridging is again forecast to build/strengthen into parts of the West next week as troughing along the West Coast slowly drifts offshore. This will allow another stretch of warm/hot weather and records highs to expand over the Pacific Northwest southward to the Desert Southwest by late in the week. In turn, this will promote downstream troughing over the Great Lakes/Midwest as another frontal boundary pushes through the region with showers and storms. ...Guidance/Predictability Evaluation... A composite blend of best clustered model solutions of the 18 UTC GFS/GEFS mean and the 12 UTC ECMWF/ECMWF ensemble mean along with the 01 UTC National Blend of Models seem to offer a good basis for the day 3-5 (Wednesday-Friday) forecast period in a pattern with above average continuity and predictability. The WPC product suite was then primarily derived from still compatible GEFS/ECENS means and the NBM next weekend in a period with slowly growing forecast spread and uncertainty. Developing differences into next weekend included details with the hot ridging over the West, but especially with the amplitude and longitudinal focus of downstream upper trough amplification over the east-central U.S.. The 00 UTC GFS/ECMWF/Canadian solutions have converged upon a more common/amplified trough solution favorably aligned with the aforementioned ensemble means, bolstering forecast confidence at these longer time frames. ...Weather Highlights/Hazards... As an upper low just off northern California slowly weakens/lifts northward, strong ridging will build over the West, allowing temperatures to climb to 15-25+ degrees above normal in Washington/Oregon next weekend, and more generally 5-15 degrees above normal along and west of the Rockies. Record highs are likely for an expanding area late in the week as temperatures near and over 100F will focus in interior sections of the West. Rainfall will be little to none throughout the region. In the East, By later week, an increasingly robust/amplified upper trough digging from south-central Canada will carry a wavy and fortified cold front southeastward into the east-central U.S. as a warm front lifts through and out of the southern Plains, inviting moisture return northward. Showers and storms will significantly increase in coverage and intensity later week along and ahead of the front and near areas of low pressure, focused over the Upper Midwest/Corn Belt into the Ohio Valley/Appalachians. 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