Extended Forecast Discussion NWS Weather Prediction Center College Park MD 356 PM EDT Wed Apr 29 2020 Valid 12Z Sat May 02 2020 - 12Z Wed May 06 2020 ...Much above normal temperatures for the South... ...Parade of active weather systems to affect the Nation... ...Guidance/Predictability Assessment... The start of the medium range period (Sat May 2) showed above average consistency and continuity from the previous cycle such that a near equal multi-model blend was incorporated between the 00Z ECMWF, 00Z UKMET, 00Z CMC, and 06Z GFS. Beyond Day 4, typical model biases were noted with the faster progression seen in the GFS compared to the ECMWF/UKMET/CMC suite. However, the 06Z GEFS mean appeared useful and was utilized along with the 00Z ECENS mean increasingly in the model blend through day 7. This adjusts the forecast toward the latest guidance while maintaining WPC continuity. ...Weather/Hazard Highlights... A pesky closed upper low/trough will slowly move over the Northeast Saturday. The amplified and cooling system will support lingering moderate rains and windy conditions across the region as deepened moisture wraps inland around a developing coastal low. The exiting storm will pose a weekend maritime hazard. Upper ridging and above normal temperatures will spread from the Southwest/Rockies through the South this weekend and linger early next week. Temperatures will range up to 10-20F above normal, with some daily records possible, especially over the southern Plains. Upper trough and jet energies will amplify/dig from the north-central U.S. through the East this weekend. Rainfall may focus from the central Rockies/Plains through the Mid-MS/OH Valleys through the central Appalachians. Dynamics, instability and progressive frontal push may support some organized strong to severe convection with locally heavier downpours, but smaller scale details remain less certain. Upstream, robust eastern Pacific trough energy/height falls will work inland across the West Sun into Mon and spread a swath of moderate precipitation mainly from the Northwest through the northern Rockies. Favored higher elevations may see periods of enhanced snow. The dynamic system should emerge over the north-central U.S. Mon before digging into the East mid next week. Forecast spread and guidance uncertainty quickly increases at these longer time frames, but the larger scale flow suggests that an associated frontal system and lead instability may favor a risk of additional strong to severe convection with some organized heavy convective downpours from the north-central Plains southeastward through the MS Valley through the Appalachians. Schichtel/Taylor 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/Southern Plains, the Middle/Lower Mississippi Valley, the Tennessee Valley, the Southern Appalachians, and the Ohio Valley, Mon-Tue, May 4-May 5. - Heavy rain across portions of the Upper Mississippi Valley and the Northern Plains, Sun-Mon, May 3-May 4. - Heavy rain across portions of the Southern/Central Appalachians, the Middle Mississippi Valley, the Ohio Valley, and the Tennessee Valley, Sat-Sun, May 2-May 3. - Flooding possible across portions of the Northeast, the Central Appalachians, the Middle/Upper Mississippi Valley, the Mid-Atlantic, the Great Lakes, and the Ohio Valley. - Flooding occurring or imminent across portions of the Southeast, the Mississippi Valley, and the Northern Plains. - Flooding likely across portions of the Southeast, the Middle Mississippi Valley, and the Northern Rockies. - Much above normal temperatures across portions of California and the Southwest, Tue-Wed, May 5-May 6. - Much above normal temperatures across portions of the Central/Southern Plains, the Central/Southern Rockies, the Central Great Basin, and the Southwest, Sat-Wed, May 2-May 6. - Much above normal temperatures across portions of the Central Rockies, the Central Great Basin, and the Southern/Central Plains, Sat-Mon, May 2-May 4. - Much above normal temperatures across portions of the Southern Plains, Sat-Tue, May 2-May 5. 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