127 FXUS02 KWBC 070510 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 110 AM EDT Thu May 7 2026 Valid 12Z Sun May 10 2026 - 12Z Thu May 14 2026 ...General Overview... An amplified mean flow pattern will persist through much of the period, tied to a closed low anchored over eastern Canada. This will bring deep cyclonic flow and shortwave energies ejecting into central/eastern U.S. This pattern will support a series of frontal passages, which will bring showers and thunderstorms along the boundaries. As the primary cold front moves southeastward, below normal temperatures will spread into eastern U.S. through Tuesday. An strengthening ridge across the western U.S. will bring well above normal temperatures that will gradually move into central U.S. by midweek. ...Guidance/Predictability Assessment... The latest model guidance remains well clustered through most of the forecast period in regard to the large-scale features of the broad troughing across eastern U.S. from the anchored low over eastern Canada and the ridge over western U.S. There are some smaller scale differences that appear amongst the deterministic models towards Day 5. The GFS seems to eject additional shortwave troughs along the eastern U.S. trough compared to the ECMWF and CMC. In addition, the models diverge a bit for the low/trough over the Pacific later in the period. Some of these differences will have an impact on sensible weather and frontal placements and progression. The WPC forecast used a composite blend of the ECMWF/GFS/CMC/ECAIFS/UKMET through the earlier portion of the period, with gradually adding more weight toward the ensemble means to compensate for timing and amplitude differences. ...Weather/Hazards Highlights... The closed upper-level low over eastern Canada will continue to support a mean longwave trough extending into eastern U.S. through the period. This pattern will bring a mature and persistent cyclonic circulation aloft and multiple shortwave energies ejecting along the base of the mean trough. Each impulse will support the progression of a strong cold front that will sweep through the eastern half of the country early in the period. The frontal passage will bring widespread showers and thunderstorms across portions of the Great Lakes, Lower Mississippi Valley/Southern Plains, Ohio Valley into the Northwest and Mid- Atlantic, with locally heavy rainfall possible along the boundary through Monday. Across the southern tier, the primary heavy rainfall threat is expected to focus near the quasi-stationary frontal boundary extending from eastern Texas through the Gulf Coast region on Sunday. Deep- layer Gulf moisture transport and weak impulses moving through the southern stream will support repeated convective redevelopment along the boundary. With flooding concerns over the area, a Marginal Risk has been continued for Day 4/Sunday ERO across parts of the Southeast. On Monday, the boundary weakens as the primary cold front moves into the area. As the primary cold front moves closer to the East Coast, much of the Plains and Mississippi Valley will see a short- lived drying trend by Monday with the front clearing the East Coast by Tuesday. Farther west, another frontal boundary begins to form over the Northern Tier as a potential clipper system, bringing chances for showers and thunderstorms across the northern Plains into the Upper Midwest, and eventually the Great Lakes and Northeast. In addition, deep boundary layer mixing may bring somewhat gusty winds across the Rockies and Plains through the period. Temperatures will continue to trend below average across eastern U.S., as the primary cold front pushes southeastward through Monday. Across western U.S., a ridging pattern will bring well above highs through midweek, and will push eastward into central U.S. by Tuesday. Record tying/breaking highs will expand from California into Southern Plains on Tuesday. In addition, some of the high temperatures across portions of central California Valleys and Desert Southwest will reach Moderate to Major HeatRisk levels by Monday into 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 $$