Extended Forecast Discussion NWS Weather Prediction Center College Park MD 245 AM EDT Tue Oct 05 2021 Valid 12Z Fri Oct 08 2021 - 12Z Tue Oct 12 2021 ...Pattern Overview and Weather/Hazards Highlights... A pesky upper low/trough will diminish over the east-central U.S. Fri into the weekend along with a widespread wet pattern wrapping from the Southeast and Mid-Atlantic back to the Great Lakes. The south-central Appalachians may offer the most runoff risk as enhanced by terrain and duration. Meanwhile, a split stream upper trough and lead frontal system working from the West to the north-central U.S. will offer an enhanced precipitation focus from the Great Basin/Northern Rockies (including elevation snows) to the Northern Plains/Upper Midwest/Great Lakes with cyclogenesis. Subsequent southern stream upper trough and surface system translation out from the Southwest may then focus moderate rainfall/convection from the south-central U.S. to the Midwest early next week in response to robust upper trough/low amplification and frontal digging back over an again unsetted and cooled West. Maximum temperatures there may decrease in some areas to 10-20F below normal to offer potential for some record values. This development would also foster widespread precipitation chances over the West to include enhanced mountain snows. Downstream, a warming Plains upper ridge later week shifts over the east-central U.S. next week. WPC web links listed below provide more specific information on the surface/500mb pattern and sensible weather/hazards. ...Guidance Evaluation/Preferences... The models seem to offer reasonably well clustered guidance Fri/Sat considering flow complexity and a composite blend of the latest GFS/ECMWF/UKMET/Canadian, the National Blend of Models (NBM) and WPC continuity seems to offer a good forecast basis and detail consistent with a mid-larger scale pattern with average to above average predictability. The compatible 12 UTC GEFS/ECMWF ensemble means and the NBM may prove a more suitable blend days 5-7 (Sun-next Tue) considering model run to run variances with embedded systems and weather specifics, but forecast spread at these longer time frames may still equate to a pattern with average to above average predictability. Schichtel 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, 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