Extended Forecast Discussion NWS Weather Prediction Center College Park MD 410 PM 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 across the Southeast and southern Appalachians this weekend into early next week... ...Guidance and Predictability Assessment... The WPC medium range product suite was primarily derived from a blend of the 06z GFS/00z ECMWF/00z UKMET model guidance combined with the 06z GEFS Mean and 00z ECMWF Ensemble Mean. This maintains good WPC continuity. ...Southeast/Appalachians/Eastern Seaboard... An amplified southern stream upper low/trough and wavy surface system moves slowly across the Southeast and eastern Gulf coast/Florida into early-mid next week and will continue to tap deep moisture from the Gulf of Mexico/Atlantic to fuel a persistent 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 a new frontal wave developing from the mid Atlantic to the northeast on day 7 Thu 13 Jun. Several inches of rain are possible in portions of the Southeast, southern Appalachians, and Gulf coast/northern Fl. ...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 the Atlantic that offers a risk of a widespread rainfall across the coastal mid Atlantic up to the northeast, with locally heavy amounts possible. There is an increasing guidance signal for upstream trough amplification over the Upper MS Valley, Great Lakes and Ohio Valley next Tue 11 Jun-Wed 12 Jun, with cyclogenesis expected. This would result in a new round of rain across the Ohio Valley to the Great Lakes. ...Southern Rockies/High Plains/Rio Grande Valley... A series of upper impulses crossing the southern Rockies/High Plains generate favorable upper difluence and upslope fetch/trailing surface front convergence that leads to generation of showers in the southern Rockies and high Plains, possibly moving down into the Rio Grande valley of interior Texas in the Sunday-Tuesday time frame. ...CA/Pacific Northwest/Great Basin/Northern Rockies... The high amplitude deep layer ridge in the western US leads to a large area of above normal temperatures with forecast high temperatures 10 to 20 degrees above normal across northern CA and NV/OR/WA/ID on days 4-5. The ridge gradually deamplifies days 6-7 so the airmass moderates starting day 6 Wed 12 Jun in western WA/OR/northwest CA, and even come close to normal on day 7 in these areas. Interior portions of the west have 5 to 10 degrees above normal day 7 Thu 13 Jun. Petersen 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 Southeast, Mon-Tue, Jun 10-Jun 11. - Heavy rain across portions of the Central/Southern Appalachians, the Tennessee Valley, the Mid-Atlantic, the Southeast, the Great Lakes, and the Ohio Valley, Sun-Wed, Jun 9-Jun 12. - Flooding possible across portions of the Central/Southern Plains, the Middle/Lower Mississippi Valley, and the Ohio Valley. - Flooding occurring or imminent across portions of the Plains, the Mississippi Valley, the Great Lakes, the Northern Great Basin, and the Ohio Valley. - Flooding likely across portions of the Central Plains, the Northern Rockies, and the Northern Great Basin. - Excessive heat across portions of the Lower Mississippi Valley and the Southern Plains, Sun-Mon, Jun 9-Jun 10. - Much above normal temperatures across portions of California, the Central Great Basin, the Pacific Northwest, the Northern Rockies, and the Northern Great Basin, Mon-Thu, Jun 10-Jun 13. 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