Extended Forecast Discussion NWS Weather Prediction Center College Park MD 335 AM EDT Fri Oct 24 2025 Valid 12Z Mon Oct 27 2025 - 12Z Fri Oct 31 2025 ...Heavy rain possible up the East Coast next week... ...Overview... The medium range pattern over the lower 48 next week looks very amplified and active. Deep troughing over the West will continue to bring unsettled cool conditions to the region through Monday, with a compact upper low over the Northeast, and a weakening low across the Mid- South. Energy from these three systems will interact into mid week eventually resulting in a likely large and deep upper low over the Eastern U.S. which will bring widespread rain to the Ohio Valley, Appalachians, and East Coast. Weaker shortwaves and frontal boundaries will keep particularly the Pacific Northwest wet through much of the next week. ...Guidance/Predictability Assessment... Model guidance is in reasonably good agreement through about Tuesday, but quickly become more and more uncertain regarding the specifics of the developing East Coast low later in the week. There is a lot of uncertainty surrounding how the energy from the west- central U.S. trough and initial Northeast low will interact. The GFS and ECMWF have better support from the ensemble means in showing interaction of these two features and a due east track of the new resulting low from the Ohio Valley to the Northeast next Wednesday-Friday. The CMC (and to some extent the UKMET) keep the two features separate with a further south or southeastward track of the upper low through the Mid-South to Southeast. This affects any kind of coastal low development off the East Coast, with the EC and ECENS continuing to favor more development. The WPC forecast favored the EC/GFS solutions which was closest to continuity. Tropical Storm Melissa in the Caribbean is forecast to be a slow moving major hurricane by the start of the medium range period near Jamaica. Its track is also highly influenced by the developing trough/low over the East next week, with the CMC furthest west before it gets pushed over the Bahamas and out to Sea. The GFS remains much faster than the consensus. Despite the uncertainty in the exact track, Melissa is not expected to bring much if any impacts to the U.S. East Coast outside of some waves and rip currents, but given dependence on the Eastern U.S. evolution, Melissa is worth monitoring for any potential changes to the forecast. The WPC forecast will follow the official forecast track from the National Hurricane Center. The WPC forecast begins with a blend of the 18Z GFS, 12Z ECMWF, and lesser proportion of the 12Z UKMET. Into the mid and late period, quickly increased the proportion of ensemble means to 70 percent of the blend by Day 7 given the increasing spread. ...Weather/Hazards Highlights... With a low pressure system over the Mid-South by Monday, and another possibly developing offshore, rain chances are forecast to spread into the Appalachians and Carolinas into the southern Mid- Atlantic. Continued a Marginal Risk in the Day 4/Monday ERO to include not just the coastal rain but back into the south- central Appalachians that can be sensitive to heavy rain causing flash flooding. As these features interact with additional energy to the west, more rain looks to overspread the Ohio Valley and Appalachians to Mid- Atlantic by midweek, with Marginal Risk also in place on the Day 5/Tuesday ERO for the Mid-Atlantic region. There remains a lot of uncertainty in amounts and placement of this rain and forecast details are likely to change given the model spread at this point. Expect rain to continue tracking up the East Coast Wednesday-Friday. Troughing across the Northwest and the tail end of an atmospheric river will lead to precipitation there, including higher elevation snow that will likely be heavy in the Cascades and perhaps into the northern Rockies into Monday, with 1 to 2 feet of snow possible. Energy from the western trough should push a front through the north-central U.S. for rain chances in the Dakotas and Upper Midwest especially on Monday. This rain looks to have low rates given lack of instability, and since this does not tend to be an area that is sensitive to flooding, do not have any sort of ERO risk in the outlook at this time. Gusty winds are possible in the north- central Rockies to Plains early next week with this system as well. Additional weaker shortwaves/fronts into the West will keep rain and mountain snow chances in the forecast for particularly the Pacific Northwest through much of the week. Cooler weather will be in place across the West early next week, especially the Northwest through Monday where highs are forecast to be 10 to 15 degrees below average. Temperatures should moderate after Monday back to normal or even a little above normal. Meanwhile, parts of the Plains will be near to above average early next week before a cool down midweek as colder high pressure builds in behind a cold front. Much of the East Coast region should generally be slightly below average through most of the forecast period. 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