Extended Forecast Discussion NWS Weather Prediction Center College Park MD 255 AM EDT Sat Oct 25 2025 Valid 12Z Tue Oct 28 2025 - 12Z Sat Nov 01 2025 ...Heavy rain possible for the eastern U.S. next week... ...Overview... Models continue to advertise an amplified and active upcoming medium range pattern. Deep troughing over the Central U.S. to start the period on Tuesday looks to close off an upper low as it drops south/southeastward into the Mid-South. Meanwhile, a retrograding upper low over the Northeast may interact with the southern low resulting in possibly a large closed upper low (or at the very least amplified troughing) into the East next week and possible coastal cyclogenesis and a heavy rainfall threat. Upper ridging will build over the interior West through the period with weak shortwaves into the Pacific Northwest. ...Guidance/Predictability Assessment... The latest guidance shows good agreement the first day or two of the period, but quickly diverge with the pattern specifics in the East later next week. There is general agreement on some form of amplified troughing or a closed low over the East but the evolution of that low and interactions with the retrograding low over the Northeast are highly variable. Compared to a day ago, guidance has trended south with an upper low that forms out of the West-Central U.S. trough around Wednesday. The GFS and CMC are the farthest south with it near the Gulf Coast later next week, and the ECMWF (and ECENS) are still on the north side with much more interaction with energy from the Northeast low. This of course, has major impact on the QPF amounts and distribution across the East next week, and the WPC forecast more or less stuck close to the NBM for the sensible weather grids amidst so much uncertainty. Compared to WPC continuity, QPF is further south/slower to exit the East this cycle. New 00z guidance generally holds with their previous runs but both the GFS and CMC are slightly north of their previous positions of the upper low over the South. The WPC forecast tonight was able to use a majority deterministic guidance the first half or so of the period but quickly transitioned to heavily weighted with the ensemble means Days 5-7. Meanwhile, Tropical Storm Melissa in the Caribbean is forecast to be a slow moving major hurricane by the start of the medium range period near or over Jamaica. Its track is also highly influenced by the developing trough/low over the East next week. The trend continues to be for a track well off the East Coast, but Melissa may get picked up by the trough/low as it exits the Northeast late next week and pulled back in towards the Canadian Maritimes. The CMC was most aggressive with this solution with the GFS continuing to be much faster than consensus. Melissa continues to be worth monitoring for any potential changes to the forecast. The WPC forecast will follow the official forecast track from the National Hurricane Center. ...Weather/Hazards Highlights... Developing low pressure over the Mid-South by Tuesday will continue to spread rainfall ahead of it through the Carolinas and into the Mid-Atlantic Tuesday into Wednesday. For Tuesday, QPF amounts do not seem heavy enough to warrant a marginal risk on the ERO either in the East or farther west into the Ohio Valley/Midwest region. On Day 5/Wednesday, as the upper low deepens, it may pull more tropical Atlantic moisture into the Carolinas/Mid-Atlantic region and back into the Southern Appalachians, but with a lot of uncertainty on the amounts. Given how sensitive the Appalachians are, opted for a marginal risk over that region for the Day 5 ERO. Areas closer to the coast will need to continue to be monitored. With potential coastal low development next week, rainfall will move northward with time, with heavy rainfall possible, but still a ton of variability on the amounts and timing. The Pacific Northwest should see rounds of rain and mountain snow chances through next week as shortwaves and fronts move through. Wednesday and Thursday may have a relative break before a renewal of perhaps heavy amounts late week. Temperatures across the West will trend warmer with time next week, as upper ridging builds. Temperatures across especially the central and northern High Plains could be 10 to 20 degrees above normal by next Saturday. Meanwhile, across the South and into the Mid- Atlantic may be well below normal underneath a developing upper low, but moderate with time as the low lifts through the East. Santorelli 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 (QPF), excessive rainfall outlook (ERO), winter weather outlook (WWO) probabilities, heat indices, and Key Messages can be accessed from: 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