Extended Forecast Discussion NWS Weather Prediction Center College Park MD 359 PM EDT Thu Apr 01 2021 Valid 12Z Sun Apr 04 2021 - 12Z Thu Apr 08 2021 ...Large Scale Pattern, Guidance Preferences and Predictability Assessment... ...Weather Pattern Overview... An upper level low will be slow moving east of New England while another trough amplifies along the West Coast and moves slowly inland. The downstream ridge over the central US will lead to warm and dry conditions for much of the central and southern U.S., and some precipitation for the West and the northern tier states. The models and ensembles start showing differences in first across the eastern Pacific by Sunday night. The models move an upper trough and accompanying surface front onshore and inland across the northern Rockies and Plains, early next week, continuing into the MS Valley and upper Great Lakes midweek. The differences in the timing and phasing of the upper trough among the 00z ECMWF, 00-06z GFS, 00z UKMET, and 00z Canadian global led to low weighting to any one model solution plus blending with the ensemble means from each of the 00z ECMWF/00z Canadian/06z GEFS. ...Sensible Weather and Potential Hazards... Precipitation coverage should begin to pick up in coverage across Washington, and Oregon and the northern Rockies as the upper trough progresses across these areas late this weekend into early next week. As the trough moves across the plains into the MS Valley, upper Great Lakes and Ohio Valley mid week, then precipitation will occur in tandem with the upper trough progression. None of the current models has a forecast of particularly heavy snow or rain. Very warm temperatures are forecast for much of the central U.S. over the weekend, making it feel more like late May or even early June. Afternoon high temperatures will likely be on the order of 15 to 30 degrees above normal. Highs are forecast to reach the low to mid 80s across portions of the central Plains Sunday and Monday, then cooling by Wed and Thu Apr 8th as the upper trough moves through. High temperatures are forecast to be well into the 90s for the lower elevations of the Desert Southwest with perhaps some daily record highs. Some 100 degree readings are becoming more likely for the hotter desert locations. A slow cooling trend is expected for the West Coast as the upper trough/low moves through and cloud cover increases. Petersen/Hamrick Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php Hazards: - Flooding possible across portions of the Southeast and the Tennessee Valley. - Flooding occurring or imminent across portions of the Middle/Lower Mississippi Valley, the Ohio Valley, and the Tennessee Valley. - Much above normal temperatures across portions of California and the Southwest, Sun-Mon, Apr 4-Apr 5. - Heavy rain across portions of the Central/Southern Appalachians, the Ohio Valley, and the Tennessee Valley, Thu, Apr 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