Extended Forecast Discussion NWS Weather Prediction Center College Park MD 232 AM EDT Sun Jun 06 2021 Valid 12Z Wed Jun 09 2021 - 12Z Sun Jun 13 2021 ...Locally Heavy Rainfall Next Week Across Tennessee/Ohio River Valleys and Central Appalachians... ...Much Above Normal Temperatures Continue Across the Northern Plains and Upper Midwest... ...Overview and Guidance Evaluation/Preferences... Much above normal to near record warmth will continue next week for portions of the northern Rockies/Plains and the Upper Midwest while unsettled weather associated with a weak upper level low could spell locally heavy rainfall across the Tennessee and Ohio River Valleys as well as portions of the central Appalachians to Mid-Atlantic late in the week into next weekend. Finally, a stronger storm system approaching the West Coast is expected to bring precipitation and unsettled weather to northern California, Oregon, and Washington State. The greatest model spread and uncertainty across the CONUS lies with the progression and depth of troughing over the western U.S. and how embedded shortwaves eject out into the northern Rockies and northern Plains. The latest model guidance looked reasonably clustered for this forecast cycle through much of the period, however the 05.18Z GFS was not considered at all given its much faster progression and evolution of the trough over the West. The 12Z run was much better aligned to the rest of the guidance as well as both the ECENS and GEFS means. The more amplified and slower solution is favored and this is why the faster/progressive 18Z GFS run was considered an outlier. Looking at the latest /06.00Z/ run of the GFS, it has considerably slowed down shortwave energy progression late next week and is in line more with the other deterministic and ensemble guidance, so it offers some utility in later forecasts. Elsewhere, model guidance showed average to above average predictability with ridging persistent across the southern to southeast U.S. while some troughing is forecast to drop into portions of New England and the Northeast. This will keep the northern tier and portions of the central U.S. on the more active/unsettled weather side. The WPC blend incorporated mostly 05.12Z model data consisting of the ECMWF/CMC/UKMET/GFS while introducing more of the ECENS/GEFS means late in the forecast period to account for some of the greater spread. ...Weather Highlights/Hazards... Locally heavy rainfall will remain possible across portions of the Tennessee and lower Ohio River Valleys for the middle of the work week and this unsettled weather is forecast to then spread toward the Mid-Atlantic by late in the week as it interacts with a backdoor cold front. Meanwhile, much above normal to near record warmth will continue across the northern Rockies/Plains with some periodic convective episodes as storm systems come out of the northern Rockies. A storm system approaching the West Coast will bring precipitation to portions of northern California, Oregon, and Washington State late in the week into next weekend. 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, 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