Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 PM EDT Thu Sep 22 2022 Valid 12Z Sun Sep 25 2022 - 12Z Thu Sep 29 2022 ...Brewing tropical activity to monitor from the Caribbean... ...Pattern Overview... Upper ridge amplifies over Western CONUS beginning this weekend and continuing into next week while southeastern ridge retracts. This transition will allow energetic mid-latitude and northern stream shortwave troughs to more robustly dig downstream and carve out an amplified east-central North American upper trough to focus cooler/unsettled weather and offer some connection to possible tropical activity to monitor by mid-later next week. ...Guidance Evaluation/Predictability Assessment... Model and ensemble solutions remain well clustered Sunday into Monday and a composite of the GFS/ECMWF/UKMET/Canadian along with the National Blend of Models (NBM) seems to provide a good basis for the forecast during that period, with enhanced detail consistent with a pattern with above normal forecast predictability. Forecast spread and uncertainty growth into longer time frames and tropical system differences in particular prompted a switch to forecast usage of the ECMWF ensemble mean to maintain WPC max product and NHC preference continuity next week. ...Weather/Hazards Highlights... Upper ridge amplification over the West will support generally dry and warmer than average temperatures early-mid next week and set the stage for downstream flow amplification as shortwaves across the north-central U.S. and energy from Canada carve out a cooling east-central U.S. trough. This upper trough and deepened surface low will combine to increase lead frontal and wrap-around rainfall chances from the Great Lakes through the Appalachians/Northeast/Mid-Atlantic Sunday into Monday, with lake enhanced rainfall in the wake of system passage through Tuesday. Lead hot weekend temperatures over parts of the South this weekend will then be refreshed with trailing cold frontal passage across much of the central and eastern U.S. as Canadian high pressure builds down across the broad region. The front should stall across the Gulf of Mexico and the Florida peninsula where showers and storms may increase in coverage Tuesday onward with potential influx of tropical moisture. WPC and the National Hurricane Center are continuing to monitor the tropics regarding Invest 98L, which may form into a tropical cyclone. Latest NBM tamped up qpf from overnight over the Flordia Peninsula which is consistent with the overall deterministic and ensemble guidance. Schichtel/Kebede 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