Extended Forecast Discussion NWS Weather Prediction Center College Park MD 140 PM EDT Fri Jul 29 2022 Valid 12Z Mon Aug 01 2022 - 12Z Fri Aug 05 2022 ***High Heat Sweeps East From The Northern Plains to the Northeast next week*** ...Overview... A pattern change will come to the northwestern U.S. early next week in the form of an an upper level trough and associated cold front which bring welcomed relief from the ongoing heat wave there. The northern side of the upper ridge responsible for this heat wave is forecast to push east across the central/northern Plains early next week and then the Upper Midwest/Northeast for the rest of the week. There are signs the monsoon will weaken/become more diffuse as the upper ridge shifts east next week. ...Guidance Evaluation/Predictability Assessment... Uncertainty remains with the upper low/trough lingering near the Pacific Northwest coast early next week. Like yesterday, the 12Z GFS/UKMET continued a slowing trend of the trough progression inland, and are now more in line with the 00Z CMC (particularly around Tuesday) which was chosen as the compromise deterministic model in the forecast blend between the slow/closed 00Z ECMWF and the progressive GFS/UKMET. The powerful ridge over the north-central Pacific will continue to favor troughing over the northwestern US and there is now decent agreement among the latest global models for a closed low over the BC coast by Wednesday night. This pattern would allow a broad trough over much of the rest of the CONUS with shortwave activity over the Great Lakes/interior Northeast below the gyre stalled near Hudson Bay. The resultant shortwave trough from the closed low off the Pacific Northwest is a key feature to track in future forecasts. For now, the 00Z ECMWF was limited in the forecast blend by Wednesday since its trough over the Northwest is so prominent. Ensemble means from the GEFS/CMCE/ECENS were favored for Wed-Fri (Days 5-7). ...Weather/Hazards Highlights... Anomalous heat shifts east across the northern and central Plains to the Great Lakes through the first half of next week, where daytime highs of 15-20 degrees above normal look to once again exceed 100F in many locations (though only for a day at any particular location). Temperatures then rise rise from the Ohio Valley through the Northeast in the latter half of the week as heights continue to build east. Meanwhile, slightly above normal heat and humidity continues south of a frontal system over the nation's mid-section, continuing the record hot summer for much of the southern Plains and Southeast through next week. Heavy rain remains a threat into Monday for already water-logged western parts of the central and southern Appalachians where a Slight Risk of excessive rainfall remains for Day 4. While the monsoon remains active through next week, recent guidance suggests the eastward motion of the upper ridge brings a more diffuse focus to rain across the Southwest for Monday through Wednesday, though areas less affected recently such as central Nevada do become active in this pattern. Jackson 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, experimental excessive rainfall outlook, 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/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml