752 FXUS02 KWBC 170640 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 240 AM EDT Fri Apr 17 2026 Valid 12Z Mon Apr 20 2026 - 12Z Fri Apr 24 2026 ...Overview... A fairly active weather pattern is expected as a uppper-level low and trough over Western U.S. will support cyclogenesis bringing chances for showers and thunderstorms, as well as mountain snow, over portions of Western U.S. into Northern and Central Rockies/Plain by mid-week. Chances for active weather pushes eastward into Ohio Valley/Great Lakes and Mid-Atlantic towards late week. Cooler temperatures for much of Eastern U.S. for the start of week, until above normal temperatures over Central and parts of Western U.S. pushes eastward by midweek. ...Guidance/Predictability Assessment... Models show decent agreement on large scale features of the ridge over Central U.S., troughing over Eastern U.S., and the closed low positioned off the West Coast. The uncertainty comes in towards Tuesday into Wednesday, where models diverge specifically for the system off the West Coast. The GFS continues to show a slower progression, while the CMC/ECMWF/UKMET pushes the system closer inland by late Tuesday into early Wednesday. Run-to-run variability increasing with the GFS as well. Therefore, the forecast was based on a even mult-model blend for the first portion of the period, then gradually phasing in the ensemble means and lowering the GFS weight a bit, to be able to account for some of the timing differences. ...Weather/Hazards Highlights... Increasing return flow from the Gulf will support a broad axis of moisture convergence and instability along the frontal system over the Gulf. This will favor organized convection and potential heavy rainfall for parts of the Southern Plains on Monday and gradually expanding into the Mississippi Valley and Ohio Valley by Wednesday. Late Wednesday into Thursday, the low pressure system over the High Plains will continue to shift eastward, bringing chances for rain and thunderstorms well across the Plains into the Ohio Valley, Mid- Atlantic, and parts the Great Lakes. The possibility for localized areas of flash flooding continues as the lingering frontal boundary near Texas may produce training storms and repeated convection along the boundary. Therefore, the Marginal Risk for Day 4 will continue for parts of south Texas. Meanwhile, another system will move inland from the eastern Pacific by Monday, bringing chances for rain and thunderstorms across much of the West Coast. Over higher elevations, expect chances for light to moderate snow. With the system expected to bring 1-2 inches of rainfall on Monday and the risk of runoffs and burn-scars, the Marginal Risk over parts of northern California have been maintained. Similarly, for Day 5, a Marginal Risk has been placed as an additional 1-2 inches is expected for Tuesday into Wednesday and soil moisture will likely be saturated from recent rainfall. As the cold front moves eastward, chances for accumulating snow is likely across portions of Central and Northern Rockies from Tuesday and expands into the Northern Plains by Thursday. While impacts should be mainly confined to higher elevations, some travel impacts may be possible. Temperatures will trend below average on Monday over much of Eastern U.S. and Texas as the cold front continues to depart off the coast, and high pressure begins to build. Max temperatures will be in the 60s over Texas and dipping into the low 40s across parts of the Northeast. Frost/freeze concerns will occur for Monday night for parts of the Northeast. Over much of Central and Western U.S. above normal temperatures will build ahead of the frontal system, with the Rockies/Plains seeing 15-20 degrees above average. Towards mid-week, warmer temperatures will spread across to the East Coast, while behind the frontal system, temperatures return to below normal across parts of Western U.S. 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 $$