Extended Forecast Discussion NWS Weather Prediction Center College Park MD 205 AM EDT Thu Jun 10 2021 Valid 12Z Sun Jun 13 2021 - 12Z Thu Jun 17 2021 ...Record to dangerous heat this weekend into early next week across much of the interior West/Northern Plains... ...Extreme heat possible for the Southwest next week... ...Overview... Anomalously strong upper ridge building and amplifying through the central U.S. into next week will continue the much above normal temperatures across much of the West into the Northern Plains. Record heat will be possible early next week from the Southwest to Northern Plains where the repeated days of heat will become excessive and dangerous. Troughing exiting New England will dig back into the East next week supporting a couple cold frontal passages and a chance of showers/storms. A Pacific front will push into the Pacific Northwest early next week and head into Canada. ...Guidance/Predictability Evaluation... The amplified flow pattern holding over the CONUS during the medium range period (Sunday-Thursday) has above average model predictability and forecast confidence. A 594+ dm upper high expands over the Four Corners and central Rockies next week contributing to a +3 sigma 500 mb height anomaly which is well clustered with the available deterministic guidance. Shortwave energy downstream will help carve out more troughing over the Great Lakes to Northeast, especially by Tuesday onward. A shortwave trough rounding the base of the western trough will eject into the Northern Rockies days 6-7. Finally, over the Gulf, a weakness between the Southwest and NW Caribbean ridges/highs will take a feature southwestward into Mexico, perhaps enhancing some rainfall over the open waters. With the above average model agreement, the WPC blend this cycle utilized a mostly deterministic blend compromised of the 18Z GFS and 12Z ECMWF/CMC/UKMET with some inclusion of the ECENS/GEFS for day 7 to account for some slightly higher model spread. ...Weather Highlights/Hazards... The upper ridge over the central U.S. will keep temperatures much above normal from portions of the Southwest to the Northern Rockies/Plains late this weekend through much of next week. Departures from normal of 15F to 25F will be common with daily records likely to be set Monday-Wednesday. High temperatures well into the 110s will be possible across the Southwest while upper 90s to low 100s will be possible from Utah into portions of the Northern Plains and Northern Rockies. Little relief at night is expected with nighttime lows 10F to as much as 20F above normal. The repeating days of this type of heat, especially for areas in the northern tier unaccustomed to prolonged heat waves, will become dangerous for sensitive groups. Elsewhere across the CONUS, temperatures are expected to be near to slightly above normal, perhaps a bit below normal over the Great Lakes into the Northeast next week behind a cold front. The strong/dominant upper ridge over the central CONUS will keep much of the area void of significant or heavy rainfall -- the exceptions being over the Northwest as a front moves in this weekend and possibly along the Gulf Coast to Southeast U.S. late this weekend into early next week where a frontal boundary stalls and lingers. Taylor 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