934 FXUS02 KWBC 031924 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 324 PM 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... Models are good agreement on the amplitude and location of mean troughing in the Northeastern U.S. during the medium range period. There's some uncertainty on the strength and orientation of a mid- level ridge in the Southwest between days 3-5. The timing of a mid- week East Pacific trough is in question as well as a potential split flow pattern, but things appear to consolidate and amplify over the West Coast by late next week. A general model blend consisting of the available deterministic and Ai guidance was used on days 3 and 4. Euro and Canadian ensemble means are introduced to the blend on day 5 to favor a less amplified trough in the East Pacific, which is apparent in the GFS suite. The Ai and ensemble mean guidance are favored in the days 6 and 7 blends due to agreement on the Western U.S. trough pattern. ...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 Thursday, which is reflected in the WPC Excessive Rainfall Outlook for Day4/Wednesday and 5. Heavy rainfall concerns continue into next weekend as the stationary front lingers. 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. There's some frost potential for portions of the Lower Great Lakes/Interior Northeast early Tuesday and Wednesday mornings. Across the West, upper ridging will continue to support above average 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 next week, but the persistent 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. 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 $$