607 FXUS02 KWBC 290703 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 303 AM EDT Wed Apr 29 2026 Valid 12Z Sat May 02 2026 - 12Z Wed May 06 2026 ...Overview... Several disturbances rotating around a persistent upper level closed low centered over Ontario and Quebec will help to reinforce broadly deep troughing across the eastern U.S. this weekend into next week. This pattern typical of springtime will likely keep conditions cool and unsettled across parts of the Northeast, Mid- Atlantic, Great Lakes, and Upper Midwest. Meanwhile, a weekend frontal system with plenty of moisture will threaten portions of the Southeast and Florida with heavy rain and isolated flooding concerns. Then another Pacific low tries to push inland late in the weekend into early next week, possibly bringing some low elevation rain and mountain snow showers to parts of the West. ...Guidance/Predictability Assessment... A fairly stable mid/upper level pattern is expected to persist through the medium range period, featuring a large upper low and broad troughing across the eastern U.S., and a developing Rex block across the western U.S. The latest guidance continues to have a good handle on the overall pattern, with generally only minor spatial and temporal differences amongst the varying modeling suites. Though minor, the main sources of uncertainty deal with several smaller scale waves rotating around the large parent upper low spinning over southeast Canada... in addition to how quickly the cut-off Pacific low portion of the Rex block pushes inland. Given the stable nature of the pattern and the good representation by both deterministic and ensemble guidance, the WPC forecast was produced utilizing a composite blend of the 00Z/06Z ECMWF, EC-AIFS, GFS, CMC, and UKMET. For Days 6 and 7, the blend shifted some of the weighting of deterministic models towards the EC and GEFS ensemble means. Overall, this made for a forecast that smoothed out some of the smaller scale differences, offered good stability and continuity with the previous forecast, and was in line with the National Blend of Models. ...Weather/Hazards Highlights... An occluding low pressure system pivoting across southeast Canada will continue to foster cool, breezy, and showery conditions over parts of the Northeast through the weekend. Some light snow may fall across the higher elevations of northern New England and the interior Northeast as colder air wraps in on the backside of the low, but any accumulations are expected to be minimal. Additional disturbances rotating around the primary low over southeast Canada may push a few cold fronts and chances for showers into the Upper Midwest, Great Lakes, and Northeast later this weekend into next week, keeping temperatures near to below seasonal norms. Chilly nighttime lows may also lead to frost and freeze concerns over parts of the Ohio Valley, Mid-Atlantic, and central Appalachians this weekend as well. The developing frontal system that is expected to bring heavy rain and potential flooding concerns from Texas to the Lower Mississippi Valley and Deep South Thursday and Friday will shift eastward into the Southeast on Saturday. As the frontal wave fueled by still impressive moisture and forcing tracks towards the Mid- Atlantic coast, a trailing cold front will trigger clusters of thunderstorms capable of producing heavy rainfall rates and the potential for isolated instances of runoff and poor drainage/urban flooding. While much of the region remains in significant to severe drought, dry soils may quickly become overwhelmed and have a more difficult time absorbing heavy downpours, especially if they occur over a very short period of time. As a result, the Day 4/Saturday Marginal Risk ERO was maintained from the Florida Panhandle northeastward to eastern North Carolina. Then looking ahead to Sunday, the cold front that follows in the wake of the strengthening coastal low moving out to sea may stall across Florida. Should this occur, the stalled frontal zone would then become a focus for additional heavy rain given plentiful moisture pooling along the boundary. Thus, a Day 5/Sunday Marginal Risk ERO was introduced for much of central Florida. A slow-moving Pacific low spinning off the coast of California late this weekend may try push across California and the Great Basin during the first half of next week. There remains some uncertainty with how quickly the low will advance inland, but should it do so, enough moisture will likely be drawn in to support scattered low elevation rain and mountain snow showers across the West, along with cooler temperatures following several days of unseasonable warmth. Miller 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 $$