Extended Forecast Discussion NWS Weather Prediction Center College Park MD 255 AM EDT Thu Jun 06 2019 Valid 12Z Sun Jun 09 2019 - 12Z Thu Jun 13 2019 ...Excessive Rainfall and Flash Flood/Flooding Threat to slowly spread northeastward from the Southeast through the Appalachians and Eastern Seaboard into early next week... ...Guidance and Predictability Assessment... The WPC medium range product suite was primarily derived from a composite blend of reasonably compatable GFS/ECMWF/UKMET/Canadian model guidance Sunday into Tuesday, transitioning more to GEFS/ECMWF ensemble means amid growing forecast spread. This maintains good WPC continuity. ...Southeast/Appalachians/Eastern Seaboard... An amplified southern stream upper low/trough and wavy surface system settles over the Southeast into early-mid next week and will continue to tap deep moisture from the Gulf of Mexico/Atlantic to fuel a lingering threat of heavy rain and flash flooding/flooding across the region. There is also a strong signal to lift moisture and energy northeastward across the Appalachians/Eastern Seaboard with interaction with northern stream flow and with surface frontal approach. WPC medium range QPF early next week offers widespread 1-4" areal average amounts, with heaviest totals focusing over the Southeast. Locally higher amounts remain possible in areas of cell training/back building/cell mergers and especially into favored Appalachians terrain. These values are in addition to totals expected over the next 3 days. ...U.S. Northern Tier... A amplified/cooling lead upper trough in northern stream flow will progress from the north-central U.S. to the Northeast Sunday-Tuesday. Rain/Showers will spread eastward along/ahead of the upper trough/surface frontal system and eventually entrain deeper moisture from lower latitudes and Atlantic that offers a risk of much heavier rainfall potential early next week. There is an increasing guidance signal for upstream trough amplification/surface system genesis back over the east-central U.S. through next midweek to renew lead precipitation potential. ...Southern Rockies.High Plains... A series of upper impulses riding into the southern Rockies/High Plains, favorable upper diffluence and upslope fetch/trailing surface front convergence may lead to some daily risk of moderate convection/rainfall, especially in the Sunday-Tuesday timeframe. 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