566 FXUS02 KWBC 280757 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 357 AM EDT Tue Apr 28 2026 Valid 12Z Fri May 01 2026 - 12Z Tue May 05 2026 ...Heavy rain and flooding threat increasing from Central Texas to the Lower Mississippi Valley later this week... ...Overview... A persistent upper level low spinning over southeast Canada will keep conditions cool and unsettled through the weekend into early next week. Meanwhile, a potent storm system with plenty of moisture to work with will set the stage for heavy rain and potential flooding concerns from the southern Plains to the Southeast late week into the weekend. Looking ahead to next week, another Pacific low may bring showers to parts of the Great Basin and Intermountain West. ...Guidance/Predictability Assessment... Model guidance continues to have a fairly decent handle on the evolution of an increasingly amplified blocking pattern across the lower 48 from later this week through early next week. This pattern is highlighted by a large cut-off upper low spinning over southeast Canada, with a strong shortwave sliding across the southern tier of the U.S. reinforcing broadly deep troughing across the eastern U.S. At the same time, models are in good agreement with the development of a classic Rex block along the West Coast later this weekend into early next week. While there are still some spatial and temporal differences of these pattern drivers amongst the varying model suites, the differences are small enough to still be able to form a reasonable consensus in line with the National Blend of Models. The WPC product suite was derived from a blend of deterministic and machine learning guidance, with an increase in weighting of the EC and GEFS ensemble means for the latter half of the period. This composite helped to maintain continuity while smoothing out model differences, especially later in the period. ...Weather/Hazards Highlights... An occluding coastal low pressure system pivoting from northern New England into southeast Canada will continue to foster cool, breezy, and showery conditions across parts of the Northeast Friday into the weekend. A little snow still can't be ruled out across the higher elevations of northern New England or the Interior Northeast as colder air wraps in on the backside of the low, but the risk is lower than previous days. Temperatures from the north- central U.S. to much of the eastern U.S. will run several degrees below seasonal norms over the course of the weekend, setting up the potential for nighttime frost and freeze concerns over parts of the region. Meanwhile, a potent southern stream Pacific low scooting along the U.S./Mexico border will eject into the southern Plains on Friday As this disturbance progresses eastward, it will begin to interact with a lingering frontal boundary. Anomalous Pacific and Gulf moisture overrunning this frontal zone combined with impressive dynamics and forcing from a strong upper jet will lead to the increasing potential for significant rainfall and scattered flooding concerns from Central Texas to the Lower Mississippi Valley Friday into early Saturday. Given an environment favorable for heavy rainfall, models continue to produce a growing signal for widespread rainfall totals of 2-4" with locally higher amounts possible. As a result, introduced a Slight Risk to the existing Day 4/Friday Marginal Risk ERO, covering from Central Texas to southern Arkansas, western Mississippi, and northern Louisiana. Machine learning ERO guidance hinted at the potential for a future eastward expansion of the Slight Risk which will be monitored. The risk for heavy rainfall shifts eastward into the Southeast on Saturday as a frontal wave fueled by still impressive moisture and forcing tracks towards the Mid-Atlantic coast. Despite this region currently being affected by significant drought, clusters of thunderstorms could contain rainfall rates that are heavy enough to produce runoff, especially when considering grounds and soils that may have a difficult time absorbing rain with heavy intensity. Thus, decided to introduce a Day 5/Saturday Marginal Risk ERO from the Florida Panhandle northeastward to southern North Carolina. Then looking ahead to Sunday through early next week, the cold front that follows in the wake of the developing coastal frontal wave is looking like it may stall across Florida. Should this occur, the stalled frontal boundary would then become a focus for additional heavy rain and flooding threats which will need to be monitored as we get closer. 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 $$