Extended Forecast Discussion NWS Weather Prediction Center College Park MD 327 AM EDT Sun May 31 2020 Valid 12Z Wed Jun 03 2020 - 12Z Sun Jun 07 2020 ...Hot temperatures for the West-Central U.S. and a Gulf of Mexico feature to monitor... ...Overview and Guidance/Predictability Assessment... A composite of reasonably well-clustered GFS/ECMWF/UKMET seems reasonable over the nation Wed into Thu. However, prefer to quickly switch to an ensemble mean blend later Thu through next weekend in an effort to mitigate growing smaller-scale model timing and detail differences. Zonal northern stream flow amplifies significantly into next weekend with development of West Coast and Northeast U.S. upper troughs and the blocky nature at mid-lower latitudes seems to favor the slower side of guidance spread. The models also continue to overall trend a bit slower with ejection of closed southern CA upper trough energy late week, but the GFS/GEFS remain on the faster side of the full solution envelope. Accordingly, applied much greater weighting in the WPC blend to the overall less progressive ECMWF ensemble mean in a pattern with lowering forecast predictability and continuity over time. The ECMWF ensemble mean also seems a reasonably good fit with NHC/WPC continuity over the active tropics/Gulf of Mexico. ...Weather/Hazard Highlights... The pattern/impulses should favor showers/thunderstorms mid-late week with a focus for locally moderate to heavy downpours from the Mid MS/OH Valleys to the central Appalachians/Mid-Atlantic in advance of a southward sinking cold front. Frontal passage will also act to mitigate lead warm sector heat. The wavy front extending back to the Northern Plains/Rockies will also provide a focus for instability/convection with a series of passing impulses. Maximum temperatures will remain hot across much of the west-central U.S. with a broad area of plus 10-15F anomalies and spotty record values in advance of an approaching/moderating cold front. Lead southern CA closed low ejection northeastward over the West late week will increase rainfall coverage and height falls/moisture and ample weekend West Coast upper trough amplification will further enhance potential across the West to the northern Plains. The Gulf of Mexico should be active with eastern Gulf/FL convection focusing near an old front mid-late week. WPC and NHC are also monitoring potential system development into the southern to western Gulf into next weekend. Deep tropical moisture works gradually northward to significantly enhance rainfall potential. The Canadian offers more robust development than other guidance, while the ECMWF/ECMWF ensemble mean lift a low on a more southern to western Gulf track more in line with NHC/WPC continuity than the more eastward shifted GFS/GEFS. Schichtel Additional 3-7 Day Hazards information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, 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/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml