Extended Forecast Discussion NWS Weather Prediction Center College Park MD 436 PM EDT Wed Oct 11 2023 Valid 12Z Sat Oct 14 2023 - 12Z Wed Oct 18 2023 ...Guidance Evaluation/Predictability Assessment... There is decent agreement among global deterministic guidance through this weekend with a central Plains low that weakens/opens into a trough over the Great Lakes Friday night as it joins a trough from an eastern Canadian low. Likewise with an omega high over north-central Canada and troughing off the Pacific Northwest. However, by Sunday night, the 00Z ECMWF begins to outpace its ensemble mean with an open wave approaching the Pacific Northwest where the 00Z CMC/UKMET have a slower/closed low and the 06Z GFS is farther north. Given the outpacing deterministic run, the model preference shifts from a general model blend over the weekend to one favoring the 00Z ECENS/06Z GEFS means by Monday. QPF began with the 13Z NBM with timing/magnitude blending with the ECMWF and GFS through Sunday, then it was more of an effort to reduce the NBM coverage both east and west early next week due to uncertainty and a lack of signal for excessive rain. The 12Z GFS features a sharper trough approaching the Pacific Northwest on Monday which is more in line with the non-ECMWF consensus. ...Weather/Hazards Highlights... A low tracking east from the Great Lakes weakens into a trough this weekend as it reaches stalls over the Northeast. Moderate to localized heavy rains are forecast across the north-central Mid-Atlantic. A Marginal Risk is maintained for the Day 4/Saturday Excessive Rainfall Outlook with a bit of a trim from the north based on the latest guidance. Meanwhile, a complex series of systems will act to amplify an eastern Pacific upper trough position and also bring moisture to the Pacific Northwest Coast to fuel moderate to possibly heavy precipitation for favored terrain of the Cascades in a wet period late weekend/next week. However, low enough precipitation rates warrant no excessive rainfall risk for Day 5/Sunday. The cold front sweeping across the eastern U.S. Saturday into Sunday will bring temperatures generally 10 to 15 degrees below normal, including south Florida which will see near record high temperatures in the low to mid 90s through Saturday. Meanwhile, a building ridge over the west-central U.S. brings temperatures generally 5 to 10 degrees above normal west from the Rockies to the eastern lee of the Cascades. 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 Hazards: - Heavy rain across portions of the Lower Great Lakes, the northern Mid-Atlantic, the Northeast, and the Central Appalachians, Sat, Oct 14. - Flooding possible across portions of the Northern Plains. - Frost/freeze across portions of the Central Rockies, the Central High Plains, and the Southern High Plains, Sat, Oct 14. WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation forecast, excessive rainfall outlook, winter weather outlook probabilities, heat indices and Key Messages 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 https://www.wpc.ncep.noaa.gov/#page=ovw