400 FXUS02 KWBC 021925 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 325 PM EDT Fri Oct 2 2026 Valid 12Z Mon Oct 05 2026 - 12Z Fri Oct 09 2026 ...Lingering Gulf Coast/Southeast U.S. Excessive Rainfall/Flooding threat Monday into Tuesday... ...Long Duration Late-Season Heat Wave Expected for California... ...Guidance/Predictability Assessment... Models continues to maintain good agreement on the large-scale evolution of an amplified northern-stream into the eastern U.S., with a series of frontal boundaries settling southward across the north-central and eastern states. There does remain some forecast uncertainty increases with the positioning of the frontal boundary across the Gulf Coast/Southeast, especially towards mid-week, which affects the location for the heaviest precipitation. The ECMWF seems support a faster southeastward progression of the precipitation axis, while the GFS maintains the axis further north. Using a model blend of the deterministic, ensemble, and AI guidance, seems to smooth some of the timing and amplitude differences across the Gulf Coast/Florida. Elsewhere, there are some timing differences of shortwaves acting to reinforce the Eastern U.S. trough. Greater uncertainty arises late week as another shortwave approaches the Northwest. The GFS has consistently been a bit faster and more amplified with this feature which seems to show a faster break down or suppression of a strong ridge over the West earlier in the week. The WPC forecast trended more towards the ensemble means with some inclusion of the ECMWF and EC-AIFS guidance, maintaining good continuity with the previous WPC forecast as well. ...Pattern Overview and Weather/Hazards Highlights... A broad trough extending across the eastern U.S. will continue to support a slow-moving frontal boundary along the Gulf Coast into the Southeast. Deep moisture from the Gulf will remain pooled along the boundary, supporting locally heavy rainfall across the central Gulf Coast into Florida. Repeated rounds of high rainfall rates will lead to excessive rainfall/flash flooding threats across south Texas and portions of the Gulf Coast into the Southeast and northern Florida, which is reflected on the Day4/Monday Excessive Rainfall Outlook with a Marginal Risk area. Flood risk continues for northern Florida through Day5/Tuesday. Towards mid- week, chances for showers and thunderstorms continues as the frontal boundary stalls across the Gulf Coast into Florida. The axis of greatest rainfall will continue to gradually shift south and east as the high pressure strengthens over the eastern states and a dry airmass builds behind the front. Farther north, a series of northern-stream shortwaves will eject frontal passages across the northern Plains, Midwest, Ohio Valley, and Northeast. Towards mid to late week, the potential for isolated light showers may develop along the boundary, while cooler air behind the front begins to spread into the north- central and northeastern U.S.. Across the West, persistent upper ridging will maintain above- normal temperatures across much of Western U.S. into the work week. The greatest heat will remain concentrated across California and the Desert Southwest with daytime highs reaching into the 90s to low 100s. The prolonged heat will pose a risk for heat related illness, especially for those without adequate cooling and hydration, equating to extreme HeatRisk especially for the Los Angeles and San Diego population areas. See WPC's Key Messages for the California October Heat Wave for additional information. Santorelli/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 $$