939 FXUS02 KWBC 060459 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1259 AM EDT Wed May 6 2026 Valid 12Z Sat May 09 2026 - 12Z Wed May 13 2026 ...General Overview... The deep cyclonic flow regime tied to a closed low over eastern Canada will facilitate a continuation of unsettled conditions. The system will eject shortwave energies across central/eastern U.S., supporting a series of frontal passages, which will bring showers and thunderstorms along the boundaries. The remnants of a prior front will linger across the Lower Mississippi Valley into the Southeast, bringing additional rainfall to the area. Below normal temperatures will continue across the Great Lakes into the Northeast through the weekend into early next week, while a warming trend continues to push eastward across much of the Western U.S. and eventually Central U.S. by early next week. ...Guidance/Predictability Assessment... The deterministic models remains in decent agreement for the large-scale features of the ridge moving into western U.S. and the broad troughing over eastern U.S. There seems to be some differences amongst the models early in the period of a shortwave trough that moves through the southwest with the CMC showing a faster progression compared to ECMWF and GFS. On day 5, model spread increases for the timing and amplitude of the embedded shortwaves within the eastern trough and the evolution and inland progression of the ridge over the west. These differences will create some uncertainty for frontal boundary placement and sensible weather. The multi-model blend weighted toward ensemble means provides a stable solution for the variability within the deterministic models. Therefore, the forecast consisted of a even model blend of the CMC/GFS/ECMWF/ECAIFS, with less weight on UKMET as timing differences was much large than the other models. Later in the period, the ensemble means were phased in to compensate for the timing, amplitude, and evolution differences. ...Weather/Hazards Highlights... The closed upper-level low over eastern Canada will continue to bring cyclonic flow and multiple shortwave energies near the base of the mean trough. This will facilitate 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. In addition, the southern extend of a previous front will continue to stall across the Gulf Coast region, where persistent moisture pooling and weak impulses embedded in the subtropical flow could support occasional convection and heavy rainfall along the Southeast through Sunday. With flooding concerns over the area, a Marginal Risk have been introduced for Day 4/Saturday ERO across southeastern Texas, Louisiana, and Mississippi and Day 5/Sunday ERO across parts of Alabama, Georgia, and Tennessee. As 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. Over the western/central U.S., a shortwave energy will push a frontal boundary over parts of the Northern-Central Rockies/Plains, which will bring a chance for low- elevation showers and thunderstorms. With temperatures dropping to frost/freeze criteria during the overnight hours, there is a chance for high- elevation snow across the Rockies on Saturday. In addition, deep boundary layer mixing will bring gusty winds across the area through the weekend. On Monday, 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 Upper Midwest. Furthermore, wraparound moisture and embedded shortwaves will bring chances for some scattered showers across the Great Lakes into the Northeast through the period. As the cold front over the Northern Tier moves southeastward, it will usher a return of anomalous below- average temperatures across northeastern U.S. and moderate temperatures across central U.S. by Sunday. A ridging pattern will continue to move further inland over the western U.S. early in the period, bringing increasingly well above average highs through early next week. Some record- tying/breaking highs will be possible as heat reaches potentially hazardous levels across portions of the central California Valleys and the Desert Southwest by Monday into Tuesday. Well above normal temperatures push eastward into central U.S. by 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 $$