Extended Forecast Discussion NWS Weather Prediction Center College Park MD 317 PM EDT Mon Apr 24 2023 Valid 12Z Thu Apr 27 2023 - 12Z Mon May 01 2023 ...Overview and Guidance/Predictability Assessment... Guidance depicts the emergence of an omega ridge in the West and a series of troughs with an eventual deep negatively tilted upper low in the East during the medium range period. The overall synoptic pattern over the CONUS appears to have sped up since overnight. The 00z EC and 06z GFS both appear to amplify shortwave into a deep upper-level low over the Midwest this weekend into early next week, but the 00z EC splits flow with an over-emphasis on a separate piece of southern stream energy compared to the GFS, CMC and ensemble means on Sunday. Unsurprisingly, the axis of qpf associated with the 00z EC is upstream of the rest of the guidance. For our blends, we favored the GFS/GEFS suite beyond day 4 due to better run to run consistency and less ensemble member spread. On days 3 and 4 we utilized a general model blend consisting of the 00z EC/CMC/UKMET and 06z GFS. The 06z GEFS was introduced on day 5 and continued through the end of the period along with the 06z GFS and 00z ECE/CMCE. There's uncertainty in the 00z suite of ensembles about the speed of the upper low as it propagates through the East, as well as another upper trough approaching the West Coast from the Gulf of Alaska this weekend. ...Weather/Hazards Highlights... Late week main system ejection across the South/Southeast along with less certain lead impulses will act to re-focus lower atmospheric convergence/baroclinicity with a series of frontal waves. There will be several opportunities for ingredients to come together to fuel swaths of moderately heavy convective rainfall given influx of Gulf of Mexico to western Atlantic moisture and instability. Downstream, guidance has trended away from deep coastal low development. A blocky upper trough/closed low flow to the north should steadily lose influence later this week, but still favor cooled and unsettled weather/widespread light-side precipitation from the Great Lakes/Midwest though the Northeast. Meanwhile, northern stream upper trough energy remains slated to dig southeastward into the north-central U.S. late next week and then in earnest within an amplifying pattern that settles in late week/weekend coincident with upstream strong upper ridge translation and building inland across the West Coast. Run to run continuity is not stellar, but this general track would increasingly focus precipitation across the north-central states. The pattern favors development of much below normal temperatures down through the central to east-central U.S. as frontal surges of cold Canadian air sink into the U.S. with system development and overall flow amplification. Kebede/Schichtel 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 WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, experimental excessive rainfall outlook, 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/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml