FXUS02 KWBC 251945 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 345 PM EDT Sat Apr 25 2026 Valid 12Z Tue Apr 28 2026 - 12Z Sat May 02 2026 ...Heavy rain/runoff and severe weather threats from the ArkLaTex to the Tennessee Valley Tuesday may be followed by additional heavy rainfall/runoff potential across the south-central U.S. and also with a New England coastal low to monitor for Thursday/Friday... ...Guidance/Predictability Assessment... Latest guidance clustering and predictability seems above average with the mid-larger scale pattern evolution and overall main system timings and threats focus through much of upcoming medium- range time scales. A favored multi-model and ensemble mean blend should also act to mitigate wide-ranging/lingering smaller scale variances as consistent with individual feature predictability. This solution and threat messaging has good WPC continuity and remains generally in line with the National Blend of Models (NBM). ...Weather/Hazards Highlights... A trailing cold front in the wake of strong/windy low pressure system advancing through the Great Lakes into southern Canada will slide to the south and east on Tuesday, bringing a organized showers and thunderstorms to the eastern U.S.. A wave of low pressure developing near/ahead of the tail end of the front with southern stream energy ejection will become the greater focus for another round of heavy rain and possible severe weather on Tuesday from the ArkLaTex to the Tennessee Valley. Significant moisture and instability pooling along the boundary and frontal wave will likely lead to clusters of strong thunderstorms with high rainfall rates, supporting the potential for isolated instances of flash flooding. A Marginal Risk ERO remains in place for Day 4/Tuesday as a result. Additional showers and storms likely linger along and just north of the Gulf Coast and also northward along the front over the East on Day 5/Wednesday, but any flooding risk should be fairly localized given steady progression. The main frontal wave tracks to the Eastern Seaboard Wednesday into Thursday, spreading much needed enhanced rainfall into the Mid-Atlantic and Northeast. A bit of snow isn't ruled out with this activity for parts of the higher elevations of northern New England and the Interior Northeast. There is a growing signal supporting deeper coastal cyclogenesis Thursday-Saturday with wrapping/windy long-fetch Gulf/Atlantic moisture inflow/IVT into New England. Slowed pattern/system motion offers cumulative heavy rain/runoff issues. Meanwhile far upstream, a southern stream Pacific low will slowly advance inland across southern California, the Southwest, and the Four Corners states into Thursday, spreading light to moderate low elevation rain and higher elevation mountain snow into the region. As this feature continues eastward, there is a growing signal for significant rainfall/runoff issues to develop and expand/intensify over the south-central U.S. Thursday into Friday as lead Gulf return flow intersects and overruns a lingering frontal zone, with wavy eastward progression over the South/Southeast on Saturday. Miller/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 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 $$