Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 PM EDT Sat Jul 30 2022 Valid 12Z Tue Aug 02 2022 - 12Z Sat Aug 06 2022 ...Heat wave to spread from the Plains to the East next week... ...Wet Monsoonal Pattern continues for the Southwest and Great Basin... ...General Overview... A welcomed pattern change is forecast for the northwestern U.S. next week as upper level troughing and associated cold front herald an eventual return to much more pleasant temperatures. The peak summer upper ridge will in turn spread downstream to encompass much of the central and eastern U.S. with widespread hot and humid weather. Less organized areas of excessive rainfall will become the norm across much of this broad region than has been case recently, but expect lingering monsoonal flow up across the Southwest and Great Basin/Rockies. ...Guidance Evaluation/Predictability Assessment... While a general model and ensemble composite blend seems reasonable for day 3/Tuesday, the WPC medium range product suite was primarily derived from a combination of the 13 UTC National Blend of Models and the 06 UTC GEFS and 00 UTC ECMWF ensemble mean days 4-7 (Wednesday-next Saturday). This maintains reasonable WPC product continuity overall, but with a forecast that is on the slow side of the full envelope of guidance solutions that limits the bulk of eastern Pacific upper trough height falls into the Northwest Tuesday/Wednesday more than the prior forecast. This seems more reasonable as the offshore closed system is positioned between highly amplified upstream and downstream amplified upper ridges. Latest 12 UTC model trends are now even more in favor of holding eastern Pacific upper trough energies offshore, instead waiting for approach of more northern stream energies from the Gulf of Alaska by Thursday. ...Weather/Hazards Highlights... Another heat wave is expected to make weather headlines on Tuesday across the Northern Plains and Upper Midwest for Tuesday and Wednesday, with highs running on the order of 15-20 degrees above average, potentially setting some daily records. The heat then reaches the Great Lakes, Ohio Valley, and then the East Coast for later in the week as the month of August begins hot and humid. Heat indices may exceed 105 degrees for some areas. Meanwhile, temperatures will likely slowly revert to be near to slightly below normal across much of the western U.S., with the coolest readings over Washington and Oregon. In terms of precipitation, there will likely be some abatement in the coverage of heavy rainfall across much of the nation with no Slight Risk areas of excessive rainfall for Tuesday and Wednesday. There will still be plenty of monsoonal moisture in place across the southwestern U.S., but not to the extent that has been observed recently. However, this may increase again going into Friday and next Saturday with a greater coverage of showers and storms. There may also be a round of heavy showers and strong thunderstorms across portions of the Great Lakes and the Northeast ahead of a cold front towards the end of the week as instability grows in advance of northern stream upper energies. Hamrick/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, 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