Extended Forecast Discussion NWS Weather Prediction Center College Park MD 159 PM EDT Sat Aug 27 2022 Valid 12Z Tue Aug 30 2022 - 12Z Sat Sep 03 2022 ...Overview... The mid to upper level pattern over the CONUS is expected to remain amplified next week into early next weekend, featuring a strong ridge through the interior West with troughing across the eastern Pacific and portions of the northeastern quadrant of the CONUS. A sweeping cold front will move across much of the central to eastern U.S. Tuesday-Thursday and lingering near the Gulf Coast late week, ushering in drier conditions and more fall-like temperatures to portions of the eastern CONUS. Meanwhile, warm and dry conditions are expected for the West, with some high temperature records possible across the Northwest in particular. The greatest precipitation coverage and amounts are expected to be tied to the frontal passage across the central and eastern U.S., with some moderate to locally heavy rainfall possible in the Northeast Tuesday-Wednesday and across the Gulf Coast states through much of the week. ...Guidance Evaluation/Predictability Assessment... Model guidance continues to show average to above average agreement and consistency with the amplified large scale pattern consisting of the upper trough axis tracking from the Great Lakes region towards the Northeast and deamplifying through the period, while an upper high drifts over the interior West and eastern Pacific troughing lingers upstream. The easternmost trough will push a cold front through the central and eastern U.S. before it settles along the Gulf Coast. The northern part of the front has continued its trend a bit faster compared to the previous forecast, leading to a faster movement of the rain axis along and ahead of the front and lower overall precipitation forecast for the Northeast. The early part of the WPC medium range forecast was based on a blend of the deterministic 00Z/06Z GFS and 00Z ECMWF/CMC/UKMET, given the good overall model agreement. By late next week, the details of the pattern become a little more nebulous as a weakness in the upper ridge is forecast, with energy likely somewhere in the central U.S. breaking up western and eastern upper highs, but with considerable variability among models. There are also some timing and amplitude differences with a shortwave that could enter the Pacific Northwest around Friday. Overall these differences are somewhat typical for day 6-7 forecasts, so the WPC forecast gradually phased toward a blend of about half GEFS and EC ensemble means and half deterministic models by day 7, which maintained continuity fairly well. ...Weather/Hazards Highlights... The main weather feature through the period will be a cold front that progresses across the central to eastern U.S. mid to late week. Ahead of that feature, enough warm and moist air will support scattered to numerous showers and thunderstorms, some of which could be locally heavy. The greatest chances for seeing a few stronger storms and locally heavy rainfall look to be across the eastern Great Lakes into the Northeast Tuesday-Wednesday tied to the better forcing/lift with the frontal passage, as well as the Southern Plains into the Mississippi Valley where the better instability/moisture will be found mid to late week as the front lingers. The western to north-central U.S. is expected to be mainly dry, with the exception of possible showers in central and southern portions of the Rockies and High Plains by the latter half of next week. Also, a frontal passage may clip the Pacific Northwest by late week, bringing some precipitation to the Olympics and northern Cascades. The warmest temperature anomalies will be found across the Pacific Northwest into the Northern Plains next week, underneath the building upper ridge and ahead of a cold front that slips through later in the week. Highs could reach 10-20F above normal each of those days, leading to the possibility of record highs. Meanwhile, the Northeast will also see above normal temperatures on Tuesday ahead of the stronger cold front that is slated to sweep through much of the central and eastern U.S., bringing in some early fall seasonable temperatures in its wake. As the calendar turns to Meteorological Fall, much of the Upper Midwest, Great Lakes, and Northeast should see at or slightly below normal highs, with cool lows in the 40s to 50s in portions of those areas. High temperatures in particular are also expected to be below average for the Southern Plains toward the Lower Mississippi Valley with the front and rain/cloudiness in the vicinity. Tate/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, 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