Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1221 PM EDT Sun Jun 02 2019 Valid 12Z Wed Jun 05 2019 - 12Z Sun Jun 09 2019 ...A heavy rain/flash flood threat to spread slowly northeastward later this week from the south-central Plains to the lower and mid Mississippi Valley, Tennessee Valley and into the Ohio Valley... ...Overview and Weather/Threats Highlights with Guidance/Uncertainty Assessment... A split flow pattern remains evident over North America. An amplified upper-level trough in the southern stream will be kicked slowly from the Southwest toward the central Plains and will lose some amplitude during the next few days. Models and ensembles are in excellent agreement on the slow eastward progression of the upper-level trough across the Mississippi Valley toward the Ohio Valley during latter half this week. This pattern by itself would pose a heavy rain threat from the Deep South into the Mississippi Valley. The more uncertain part of the forecast continues to be with a tropical system currently over the Bay of Campeche that may strengthen and may move closer toward the western Gulf coast. Recent GFS runs have been trending toward lower pressure over the northwestern Gulf of Mexico with the center of circulation nudged progressively off the coast, but continuing to take it on a NW/NNW track toward northeastern Mexico. Much of the associated moisture is then deposited in northeastern Mexico before drawing the remaining moisture northward into the Deep South. On the other hand, the ECMWF continues to take it on a more northerly track near or along the western Gulf coast and toward Louisiana by Friday. The Canadian model and the HWRF model offer the most convective solution with the eastern-most track, taking the system faster and stronger along/off the Texas coast and into Louisiana next Thursday. With the consideration of the upper-level trough moving slowly eastward across the Plains later this week and the forecast track of the system that would favor convection to develop on the eastern side of the circulation over the Gulf of Mexico, the eastern solutions indicated by at least the ECMWF cannot be ruled out. Meanwhile, models are indicating a significant cold upper trough from the northern stream flow to move across the Northwest late this week. The most uncertain part of the forecast has to do with the amplitude and evolution of this trough, which has implications on how much and where the precipitation will be focused. The ECMWF and to a lesser extent ECMWF ensembles have been forecasting a more amplified and slower progression with the trouge than other guidance. WPC favors a solution slightly on the more amplified side of the full envelope of solutions given overall blocky hemispheric flow pattern characteristics. This would favor some June snows for the higher elevations of the northern Rockies late this week. Overall, the WPC medium range product suite was mainly derived from a 06Z UTC GFS-parallel/GEFS mean and 00 UTC ECMWF/ECMWF ensemble mean blend. Blend weightings slightly favor amplitude and shift more in favor of the ensemble means days 5-7. In this pattern there remains a growing signal in support of a heavy rainfall threat later this week from the south-central Plains to the mid-lower Mississippi Valley, Tennessee Valley and lower-mid Ohio Valley in a region already inundated with heavy rainfall and flooding issues. Kong/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