999 FXUS02 KWBC 310654 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 154 AM EST Wed Dec 31 2025 Valid 12Z Sat Jan 3 2026 - 12Z Wed Jan 7 2026 ...General Overview... Broad cyclonic flow aloft will be in place across the Great Lakes region and the Northeast going into this weekend, and the trough becomes a little less amplified as the deep low over central Canada lifts out some to the north. Meanwhile, an upper-level ridge will initially be in place across the Intermountain West, and then reach the Plains over the weekend with widespread above average temperatures. Rain and mountain snow will be commonplace across the West Coast states Friday night and going into the weekend as shortwaves and onshore flow affect the region. Across the southern tier states, a wave of low pressure develops along a frontal boundary and brings higher rainfall chances across the Southeast U.S. into Saturday. Another clipper system is likely to cross the Upper Midwest and Great Lakes into early next week. ...Guidance/Predictability Assessment... Model guidance remains in good synoptic scale agreement with the general pattern across the Continental U.S. going into the weekend east of the Rockies, with a broad upper trough over the Great Lakes and Northeast, and a ridge axis situated over the western High Plains. The latest guidance also continues to come into better agreement regarding the wave of low pressure that develops along a frontal boundary across the Southeast states and then exits the Coast over the weekend. Uncertainty increases across the western U.S. as multiple shortwaves gradually flatten the upper level flow pattern along the West Coast, and displace the ridge eastward over the Plains. The CMC became faster than the model consensus by Sunday with the main trough axis moving inland across the West, so more of a GFS/ECMWF approach was used for Sunday and beyond. Towards the end of the forecast period Wednesday, the AI guidance favors a solution closer to the ECMWF across the western U.S., so the forecast was hedged more in the ECMWF/ECENS direction for the Tuesday-Wednesday time period for fronts and pressures. The ensemble means accounted for about half of the forecast blend by that time. ...Weather/Hazards Highlights... A more active weather pattern develops along the West Coast by in time for the weekend as a organized low pressure system lifts northward with a cold front reaching the California coast. An atmospheric river will likely affect the northern California coast and move inland through Saturday afternoon, bringing the potential for 2 to 4 inches of rainfall for the lower elevations, with a secondary maxima for the eastern foothills of the northern Sierra Nevada. A Marginal Risk area will be valid here for both Saturday and Sunday. Heavy snow is likely for the higher terrain. Elsewhere across the country, an area of low pressure is expected to exit the Southeast Coast on Saturday. This quick-moving system will produce a corridor of moderate rainfall and some thunderstorms from Mississippi eastward to the coastal Carolinas, followed by improving weather on Sunday. Another clipper type system is likely to track from the Upper Midwest, to the Great Lakes and then New England Sunday into Monday. This relatively weak system is expected to produce a swath of mainly light snow and perhaps some mixed wintry precipitation along the southern portion of the track. In the wake of the clipper, some minor lake effect and upslope snowfall is likely downwind of the Great Lakes and across portions of the central Appalachians on Tuesday. Temperatures are likely to be warmer than average across a wide expanse of the country this weekend into the middle of next week, especially from the Rockies to the central and southern Plains. Highs could be 15 to 25 degrees above average from northern Texas to Nebraska, with lower 60s reaching as far north as Nebraska Sunday into Monday. The exception to the mild conditions will be from the Great Lakes to the Northeast as this region remains under the general influence of an upper trough and north of the jet stream, where highs should be 5 to 15 degrees below average, with the coldest readings across Maine. Hamrick 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 $$