Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 PM EDT Sun Aug 28 2022 Valid 12Z Wed Aug 31 2022 - 12Z Sun Sep 04 2022 ...Overview... An amplified flow pattern is expected to start the forecast period midweek, featuring strong ridging through the interior West with deeper troughing across the eastern Pacific as well as the Great Lakes into the Northeast U.S., the latter of which helps drive a cold front across much of the central to eastern U.S. mid to late week. Drier and early fall-like temperatures can be expected in its wake from the Upper Midwest to the East Coast while the West is likely to see much above normal temperatures. The cold front is forecast to settle along the southern tier of the U.S. from the Texas Gulf Coast eastward to Florida late in the week into next weekend, and this will be focus for scattered to numerous showers and thunderstorms each day, some of which could produce locally heavy rainfall. ...Guidance Evaluation/Predictability Assessment... The amplified pattern at the beginning of the period continues to promote good model agreement and run to run consistency with the overall pattern for the first half of the medium range period, as the upper high hovers around the central Great Basin with the amplified ridge to the north potentially shifting slowly east as the eastern Pacific trough digs, and the Great Lakes trough begins to flatten out somewhat. At the surface, the main cold front shows good agreement with its timing as it tracks across the central and eastern U.S. and then settles into the Gulf Coast states. Thus the first half of the medium range forecast period consisted of a deterministic model blend favoring the 00/06Z GFS and 00Z ECMWF along with lesser proportions of the 00Z CMC and UKMET. By day 5/Friday into the weekend, a couple main areas of model differences arise--a weakness in the ridge in the south-central U.S. that should support unsettled weather across Texas, and the timing of a shortwave coming into the Northwest and tracking east. No clear outliers were seen with the former, while with the latter the 00Z CMC seemed to be on the slower end of consensus, and the 06Z GFS and the 00Z EC were more agreeable with a faster track--also supported by the incoming 12Z model guidance suite. The latter part of the WPC forecast incorporated some GEFS and EC ensemble mean guidance with the deterministics to smooth out model differences, and the resulting forecast maintained WPC continuity well. ...Weather/Hazards Highlights... A cold front sweeping across the central to eastern U.S. mid to late week will be the main sensible weather feature of note across the CONUS. Ahead of it, enough warm and moist air will lift northward to support scattered to numerous showers and thunderstorms, some of which could be locally heavy across portions of New England on Wednesday where the system will have better dynamics/lift to support more organized convection. Farther south along the southward moving boundary, better instability and moisture across the Southern Plains and potentially along the Florida Gulf Coast could support intense rain rates and localized heavy rainfall. The front then is expected to settle across the southern tier of the U.S. and will be the focus for daily showers and thunderstorms, some of which could be locally heavy through next weekend across Texas eastward along the Gulf Coast. Elsewhere, the rest of the country looks to be mainly dry aside from light rain chances across central parts of the Rockies/Plains and a frontal passage possibly clipping the Pacific Northwest bringing generally light precipitation. The greatest temperature anomalies through the period will be found across the western U.S. mid to late week, particularly across the Northwest into northern portions of the Rockies/High Plains, where highs could reach 10-20F above normal, while 10-15F above normal temperatures are possible for the Great Basin and California. Daily records could be set in the West with the possibility to flirt with monthly records as well. 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. As the upper flow pattern becomes more zonal next weekend, the above normal temperatures look to spread across much of the northern tier of the U.S. with highs next weekend possibly 5-10F above normal. Conversely, the southern U.S. is likely to see near or slightly below normal temperatures through the period, particularly the Southern Plains and Gulf Coast where widespread clouds and precipitation look to keep temperatures in check. 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