988 FXUS02 KWBC 230621 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 221 AM EDT Thu Apr 23 2026 Valid 12Z Sun Apr 26 2026 - 12Z Thu Apr 30 2026 ...Overview... An amplified and progressive spring pattern continues across much of CONUS as a surface low and frontal passage moves northeastward from the central Plains into the upper Midwest and across eastern U.S., which will bring showers and thunderstorms to the area through next Wednesday. In addition, troughing over the West will shift inland, bring chances for low elevation rain and mountain snow across the Intermountain West/Rockies into the Plains. ...Guidance/Predictability Assessment... The latest deterministic model runs continue to show reasonably good agreement on the larger scale evolution through the first portion of the period. Later in the period, the GFS guidance shows a faster progression with the trough over the the South-Central Canada. The GEFS and ECENS ensemble means provides a stable intermediate solution to address timing and amplitude differences of the shortwave energy embedded within the trough over the Northern tier, as well as the Pacific energy off the West Coast. Therefore, the forecast leans towards a blend of the GFS/ECMWF/UKMET/Canadian/EC- AIFS towards the start of the period, with incorporating the GEFS/ECMWF/Canadian ensemble means after Day 4. ...Weather/Hazards Highlights... The closed upper low and trough over northern High Plains/south- central Canada will continue to slowly lift and hover over southern Canada through the period. The system will carry multiple embedded shortwaves rotating round the base of the trough, along with northern tier secondary frontal passages and Canadian high pressure onset. This will bring lower elevation rain and terrain enhanced snow across parts of the Intermountain West, Rockies and the Plains. The trough extending off the West Coast will eject shortwave energy flow eastward into the Southwest through Sunday. This will reinvigorate a round of widespread rain/mountain snows along/north of the main system track from the Great Basin to the Rockies, lingering into early next week along with a threat of strong gusty winds, especially over the south- central Rockies/high plains. A strengthening surface low and frontal boundary will move across the central Plains/Mississippi Valley into the Midwest by Monday, serving as a focus for repeated round of showers and thunderstorms into next week across the area. Strengthening southerly flow will transport warm moisture from the Gulf into the Plains/Midwest, which will support the potential for organized convection and corridors of locally moderate to heavy rainfall. The combination of large scale forcing and increasing instability along the front will support widespread clusters of strong to severe thunderstorms with the potential for locally heavy rainfall and isolated flash flooding over parts of Plains/Mississippi Valley. This flood threat is highlighted by a Marginal Risk area in the Day 4/Sunday Excessive Rainfall Outlook (ERO). The system gradually tracks into eastern U.S. by Tuesday, shifting the chances for heavy rainfall and thunderstorms over parts of Southeast and the Ohio/Tennessee Valley. This flood threat is highlighted by a Marginal Risk area in the Day 5/Monday Excessive Rainfall Outlook (ERO). Meanwhile, as the primary low deepens and tracks from the central Plains towards the Upper Midwest and Great Lakes early next week, a broad region of precipitation and strong gusty winds will develop north and west of the low/frontal system. The system will bring a mix of enhanced stratiform rain and embedded convection. Ahead of the front, above normal temperatures across the Southern Plains, Southeast, Mid- Atlantic and Great Lakes will persist ahead of the cold front until Tuesday. 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. On Tuesday, Pacific Northwest will begin to trend slightly above average as a upper ridge moves into the region. 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 $$