Extended Forecast Discussion NWS Weather Prediction Center College Park MD 402 PM EDT Tue Jun 04 2019 Valid 12Z Fri Jun 07 2019 - 12Z Tue Jun 11 2019 ...Excessive Rain and Flash Flood/Flooding Risk to Spread from the Mid-Lower Mississippi and Tennessee/Lower Ohio Valleys to the south-central Appalachians/Mid-Atlantic and Southeast... ...Guidance discussion... Guidance agrees an amplified/closed upper level features moving through the northern and southern streams of the Westerlies. The guidance showed good agreement with modest differences detail-wise which could be effectively dealt with in a blend. The medium range 500 hPa heights, pressures, and fronts were were derived from an even split of the 00z Canadian, 00z UKMET, 06z GFS, and 00z ECMWF Friday through Sunday, with increasing amounts of 00z NAEFS mean and 00z ECMWF ensemble mean being used Monday and Tuesday, eventually encompassing close to half of the blend. Most of the lower 48 grids used a more equal portion of deterministic and ensemble mean guidance. This solution maintains reasonably good WPC continuity. ...Southeast/Mid-South impacts... The southern stream member lures moisture return from the Gulf of Mexico/Atlantic, fueling a threat of heavy rain and flash flooding/flooding. There is a strong signal for a slow spread of activity Friday-Tuesday from the Mid-Lower Mississippi and Tennessee/Lower Ohio Valleys to the south-central Appalachians/Mid-Atlantic and Southeast. WPC medium range QPF advertises 3-6" areal average amounts, with locally higher amounts possible in areas of cell training/back building/cell mergers. Deepest tropical moisture is linked to a southwest Gulf of Mexico disturbance monitored by NHC whose low-level vorticity moves into the lower 48 between Wednesday and Thursday per ECMWF ensemble spaghetti plots. ...Northern Tier impacts... A significant/anomalous cooling and unsettling upper trough from northern stream flow evolves from the Northwest/West to the north-central U.S. from late this week into early next week. Guidance is converging on a more clustered forecast, bolstering confidence in widespread moderate to terrain enhanced precipitation. This includes snows for northern Rockies higher elevations of per WPC medium range winter weather outlook probabilities. Roth/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 Hazards: - Heavy rain across portions of the Northeast, the Mid-Atlantic, the Central Appalachians, the Great Lakes, and the Ohio Valley, Tue, Jun 11. - Heavy rain across portions of the Central/Southern Plains, Tue, Jun 11. - Heavy rain across portions of the Central Plains, the Lower Mississippi Valley, the Central Appalachians, the Tennessee Valley, the Middle Mississippi Valley, the Mid-Atlantic, the Southern Appalachians, the Southeast, and the Ohio Valley, Fri-Tue, Jun 7-Jun 11. - Flooding possible across portions of the Middle Mississippi Valley, the Great Lakes, and the Ohio Valley. - Flooding occurring or imminent across portions of the Plains, the Mississippi Valley, the Central/Northern Great Basin, the Great Lakes, and the Ohio Valley. - Flooding likely across portions of the Southern Rockies, the Central Great Basin, and the Southwest. - Excessive heat across portions of the Southern Plains, Fri-Mon, Jun 7-Jun 10. - Much above normal temperatures across portions of California, the Pacific Northwest, and the Northern Great Basin, Mon-Tue, Jun 10-Jun 11. - Much below normal temperatures across portions of the Northern/Central Great Basin, the Northern/Central Plains, the Northern/Central Rockies, California, and the Pacific Northwest, Fri-Sat, Jun 7-Jun 8. 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