Extended Forecast Discussion NWS Weather Prediction Center College Park MD 412 PM EDT Wed Jun 03 2020 Valid 12Z Sat Jun 06 2020 - 12Z Wed Jun 10 2020 ...Gulf Coast to Mid-South Excessive Rainfall Threat with Tropical Storm Cristobal... ...Overview and Guidance/Predictability Assessment... Model and ensemble forecast clustering remains very good through 5 both with respect to the overall pattern evolutions and amplification, as well as an emerging threat from Tropical Storm Cristobal. After day 5, the GFS and ECMWF are better clustered with the means, while the CMC closes off an upper low in the Central Plains. The ECMWF is slightly faster/east with the cold front as well as with the eventually absorption of Cristobal. Outside of this, heights will be on the rise over both the East and West coasts through the period. WPC medium range products were derived from a operational model blend for days 3-5, replacing the CMC with the ensemble means thereafter. This maintains good continuity with the overnight WPC progs as well as the latest official track for Cristobal from NHC. ...Weather/Hazard Highlights... Deep tropical moisture inflow will fuel a threat for heavy rainfall over the central and eastern Gulf Coast/FL ahead of Cristobal this weekend, reaching a frontal zone dropping into the Southeast. The approach and landfall of Cristobal early next week should increasingly focus heavy rainfall along the track across the Mid-Lower Mississippi into the Ohio Valley/Upper Great Lakes during the early part of next week. Please refer to updates from NHC on the latest official track and intensity forecasts for Cristobal. Meanwhile, a southern stream low/trough will finally eject northeastward over the West Sat and spawn Canadian Prairie cyclogenesis by Sun. This will occur as an amplified mid-upper latitude upper trough digs inland into the West. Maximum temperatures will drop to 10-20 degrees below normal from the Intermountain West to Northern/Central Rockies as a wavy frontal system pushes eastward across the western half of the nation Sat-next Wed. Locally enhanced precipitation is possible along and behind the system across the unsettled West to include some elevation snows from the Cascades/Sierra to the Northern Rockies given trough depth. Lead above normal temperatures are forecast to persist in the Plains over the weekend. In particular, the south-central High Plains should have some maximum temperatures 15+ degrees above normal. Energies reaching the n-central U.S. next week may support enhanced moisture inflow and convection/rains along the cold frontal boundary. Santorelli/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 Central Rockies, the Central Great Basin, the Northern Rockies, and the Northern Great Basin, Sat-Mon, Jun 6-Jun 8. - Heavy rain across portions of the Northern/Central Plains, the Mississippi/Tennessee Valleys, and the Southeast, Mon-Tue, Jun 8-Jun 9. - Heavy rain across portions of the Southeast and the Lower Mississippi Valley, Sat-Tue, Jun 6-Jun 9. - Heavy rain across portions of the Mississippi/Tennessee/Ohio Valleys, the Middle Mississippi Valley, and the Great Lakes, Wed, Jun 10. - Severe weather across portions of the Northern Plains, Sat, Jun 6. - Severe weather across portions of the Upper Mississippi Valley and the Northern Plains, Sun, Jun 7. - Flooding occurring or imminent across portions of the Lower Mississippi Valley, the Northern Plains, the Northern Rockies, the Middle Mississippi Valley, the Mid-Atlantic, the Southeast, the Great Lakes, and the Ohio Valley. - Flooding likely across portions of the Middle Mississippi Valley. - Much above normal temperatures across portions of the Central Rockies, the Central Plains, and the Southern Plains, Sat-Mon, Jun 6-Jun 8. - Much below normal temperatures across portions of the Northern/Central Great Basin, the Northern Rockies, California, and the Pacific Northwest, Sat-Sun, Jun 6-Jun 7. - Much below normal temperatures across portions of the Northern/Central Great Basin, the Northern Plains, and the Northern/Central Rockies, Mon, 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