758 FXUS02 KWBC 030604 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 204 AM EDT Sat Oct 3 2026 Valid 12Z Tue Oct 06 2026 - 12Z Sat Oct 10 2026 ...Persistent Heavy Rainfall threat continues across the Gulf Coast into Southeast/Florida into Tuesday... ...Long Duration Late-Season Heat Wave Expected for California... ...Guidance/Predictability Assessment... Latest model guidance continues to show a fairly well-defined large-scale pattern with the ridging across western U.S. and broad troughing extending from the northern stream into eastern U.S.. By late- week, the primary uncertainty will be the evolution of the western ridge and the interaction with the shortwave moving into the Pacific Northwest, which will impact timing and amplitude of precipitation and cooler temperatures. Most models show a good agreement of eastward movement of the ridge, but differs on how quickly the ridge shifts and the strength of the Pacific trough. Across the Southeast, models show differences within the timing and position of the frontal boundary over the Gulf Coast into Florida, which will impact the location for the highest rainfall axis. The latest ensemble guidance generally maintains the large-scale pattern, while favoring a slow eastward movement of the western ridge. Therefore, the forecast was based on a multi-model blend through midweek, with a heavier weight of the ensemble means towards late week to help mitigate the differences. ...Pattern Overview and Weather/Hazards Highlights... A broad upper trough over eastern U.S. will persist through the week, reinforcing unsettled weather across the Southeast. The primary focus for rainfall will remain along the Gulf Coast and into Florida, where a slow-moving frontal boundary will interact with deep tropical moisture. This setup is favorable for a prolonged period of showers and thunderstorms along the boundary. Repeated rounds of convection may lead to localized flash flooding risk across portions of northern Florida through Wednesday, which is reflected in the WPC Excessive Rainfall Outlook for Day4/Wednesday. The boundary is expected to remain stalled through late week, bringing daily showers and thunderstorms that may continue flash flooding risk into Thursday. Farther north, a series of northern -stream shortwaves will progress eastward from the northern Rockies/Plains towards the Midwest and Northeast. These disturbances will reinforce the broader eastern trough, which will support periodic light showers along associated frontal boundaries across the Upper Midwest/Great Lakes into the Northeast. Behind the front, cooler air will bring below normal temperatures from the Northeast into portions of the Mid- Atlantic/Southeast through Wednesday. Across the West, upper ridging will continue to support above normal temperatures, especially across California and Desert Southwest. Daytime highs are expected to reach upper 90s to low 100s, with much of southern California under a Moderate to Extreme HeatRisk.The ridge should gradually weaken and shift eastward by late week, but the persist heat will bring concerns for heat- related illness, especially for those without adequate cooling and hydration. See WPC's Key Messages for the California October Heat Wave for additional information. By late week, scattered showers may develop for the Pacific Northwest as the next shortwave approaches. 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 $$