543 FXUS02 KWBC 220621 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 221 AM EDT Wed Apr 22 2026 Valid 12Z Sat Apr 25 2026 - 12Z Wed Apr 29 2026 ...Guidance/Predictability Assessment... Model guidance remains in fairly good agreement through Day 5, particularly with respect to the evolution of the western trough and downstream surface cyclone. The latest runs of the deterministic guidance show reasonable clustering on the timing and track of the system, though the GFS remains a bit faster and slightly more progressive with the cold front. The ensembles continue to support a good consensus approach, especially after Day 5, where spread increases regarding the amplitude and timing of the Pacific energy moving towards the western U.S. Overall, the forecast maintained a multi-model blend with the GFS/ECMWF/UKMET/Canadian models, while incorporating the GEFS/ECMWF/Canadian ensemble means later in the period to smooth out some of the smaller scale differences. ...Weather/Hazards Highlights... The upper low and trough over the northern High Plains will gradually lift and settle into south-central Canada by the weekend, carrying multiple embedded shortwaves rotating around the base of the trough. This will continue to bring periods of low elevation rain and mountain snow, with locally heavier precipitation possible along favored terrain over the Intermountain West, Rockies, and into the Plains. Most accumulating snow will primarily be confined to higher elevations, with main impacts limited to high mountain passes and mountain towns, albeit spilling into the northern high Plains. In addition, strong gusty winds are expected across parts of the Southwest, Rockies, and the Plains. This Pacific system will support an eastward projection of a surface low and cold front across the Mississippi Valley into the East through the weekend. Increasing southerly flow ahead of the system will support robust moisture transport from the Gulf. This moisture combined with favorable upper-level forcing and instability, will promote a broad area of showers and thunderstorms across central/southern U.S. into eastern U.S. Organized heavy rainfall and wide spread clusters of strong to severe thunderstorms will extend from parts of the south- central Plains into the upper Midwest from Sunday into Monday and the Ohio Valley into parts of the Southeast on Tuesday, where training convection may develop along the front. The potential for locally heavy rainfall and isolated flash flooding over parts of south-central Plains and mid-lower Mississippi Valley is highlighted by a Marginal Risk area in Day 4/Saturday and Day 5/Sunday Excessive Rainfall Outlook (ERO). Persistent upper troughing over the West will maintain a cool and unsettled weather pattern, particularly across the Pacific Northwest, northern California, and the northern/central Rockies through the weekend and into the next week. The pattern will bring rounds of precipitation, with the heaviest totals favored along coastal ranges and windward mountain slopes. Lower elevation will primarily fall as rain, while higher elevation will see periods of late- season mountain snow as post- frontal cold air filters down into the West. Another southern stream of Pacific energy will approach the West Coast, which may reinvigorate another round of widespread rain/mountain snows along/north of the main system track from the Great Basin to the Rockies, lingering there into early next week. As the primary low deepens and tracks from the central Plains towards the Upper Midwest and Great Lakes by Monday, a broad region of precipitation and strong gusty winds will develop north and west of the low and frontal system. The system will bring chances for a mix of stratiform rain and embedded convection with periods of enhanced rainfall along central and eastern U.S. Above normal temperatures across the Southern Plains, Southeast, Mid- Atlantic and Great Lakes will persist ahead of the cold front until Tuesday when the Upper Great Lakes transition to cooler temperatures. Meanwhile, below average temperature continue for much of the West and Northern/Central Plains under the troughing through Monday. Moderate temperatures across the Central U.S. return on Tuesday. Oudit 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 forecast, excessive rainfall outlook, winter weather outlook probabilities, heat indices and Key Messages 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 https://www.wpc.ncep.noaa.gov/#page=ovw $$