612 FXUS02 KWBC 041953 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 353 PM EDT Sun Oct 4 2026 Valid 12Z Wed Oct 07 2026 - 12Z Sun Oct 11 2026 ...Excessive rainfall threat ramps up once again across Central Gulf Coast and Southeast on Friday... ...Heat wave in California begins to weaken on Thursday... ...Guidance/Predictability Assessment... Models continue to be in good agreement on the evolution of transient shortwave energy propagating through the base of a mean trough in Southeast Canada/Northeastern U.S.. There continues to be some uncertainty surrounding the strength of the East Pacific/Southwestern U.S. ridge mid-week. This might be influenced by the approaching upstream trough and the model dispersion regarding its evolution, with some suggesting it'll split into two separate streams and another camp keeping it phased as it approaches the West Coast. The GFS suite is in the split flow pattern, while the Euro, Canadian and UKMET suites are in the phased trough camp. A composite blend of the available non-GFS deterministic and Ai guidance was sufficient on day 3, followed by a deterministic Euro/CMC and ECAIFS on day 4. The Euro suite and ensemble means were used on day 5 and means were favored through the end of the period. ...Pattern Overview and Weather/Hazards Highlights... The large-scale pattern through the period will feature a pronounced mean trough over eastern U.S., ridging over Western U.S., and troughing over the Eastern Pacific. At the surface, a slow- moving frontal boundary should remain draped across the Gulf Coast and Southeast/Florida through the weekend. Deep tropical moisture will spread north from the Gulf and interact with the boundary leading to repeated rounds of showers and thunderstorms, particularly across Florida and adjacent portions of the Southeast. Training convection and high rainfall rates could produce locally excessive rainfall, particularly where storms repeatedly occur. Therefore, WPC Excessive Rainfall Outlook continues to highlight a Marginal Risk for portions of Florida on Day 4/Thursday. The greatest heavy- rain potential should gradually shift with the position of the front, but Florida remains the favored area for prolonged convection through Thursday. By Friday, the axis of heavy rainfall shifts westward along the Gulf Coast and eventually inland into the Southeast on Saturday. Guidance has trended wetter for the Gulf Coast and Southeast next weekend with a corresponding increased potential for heavy to excessive rainfall. Across the Midwest into the Northeast, the persistent upper trough should maintain generally cooler conditions. Periodic shortwaves rotating through the trough may produces areas of light showers, particularly near frontal boundaries. Farther west, upper ridging should continue to support above average temperatures. Highs in the upper 90s to lower 100s will remain possible across portions of the Southwest and southern California. Warm overnight temperatures will also limit relief from the heat, leading to heat-related illness concerns especially for those without adequate cooling and hydration. Extreme heat warnings are in effect for portions of SoCal, while heat advisories are in effect for parts of Central and Northern California. See WPC's Key Messages for the California October Heat Wave for additional information. The ridge should gradually weaken, while the eastern Pacific trough becomes more amplified later this week. Additionally, as the trough continues to move inland, precipitation chances increases into the weekend over Pacific Northwest into the Northern Rockies. Kebede/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 $$