Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Wed Jun 05 2019 Valid 12Z Sat Jun 08 2019 - 12Z Wed Jun 12 2019 ...Excessive Rain and Flash Flood/Flooding Threat to slowly spread across the Mid-South and Southeast into the Appalachians/Mid-Atlantic this weekend into early next week... ...Guidance... The WPC medium range product suite was primarily derived from a composite blend of the compatable GFS/ECMWF and Canadian models this weekend, transitioning to GEFS/NAEFS and ECMWF ensemble means next week amid growing forecast spread. This solution maintains good WPC continuity. ...Mid-South/Southeast/Appalachains Impacts... A slow moving/amplified southern stream upper trough and surface system will lure deep moisture return from the Gulf of Mexico/Atlantic, fueling a prolonged threat of heavy rain and flash flooding/flooding. There is a strong signal for a slow spread of activity Saturday-Tuesday from the Mid-South and Southeast to the Appalachians/Mid-Atlantic. WPC medium range QPF advertises 3-6" areal average amounts, with locally higher amounts possible in areas of cell training/back building/cell mergers and favored southern Appalachians terrain. Deepest tropical moisture is linked to a Gulf of Mexico disturbance now off southern Texas that remains monitored by NHC. ...U.S. Northern Tier Impacts... A significant/anomalous cooling and unsettling upper troughing in northern stream flow evolves from the Northwest/West, north-central U.S. and eastward this weekend into early next week. Guidance has overall recently converged on a more clustered forecast, bolstering confidence in widespread moderate to terrain enhanced precipitation. This includes weekend snows for northern Rockies higher elevations of per WPC medium range winter weather outlook probabilities. Rain potential will spread eastward along/ahead of the main upper trough/surface frontal system and eventually entrains deeper moisture from lower latitudes/Atlantic for the East early next week. 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