306 FXUS02 KWBC 031947 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 247 PM EST Sat Jan 3 2026 Valid 12Z Tue Jan 06 2026 - 12Z Sat Jan 10 2026 ...Overview... Quasi-zonal flow over the CONUS (with progressive north-central to northeastern U.S. clipper systems) at the start of the medium range period Tuesday will turn increasingly more amplified by late week into next weekend. Southern stream troughing off the West Coast may close off into an upper low off California before it moves into the Southwest midweek and weakens in favor of additional energy diving down the West Coast late week. This energy should help develop deeper troughing moving through the West into the Central U.S., with a strengthening ridge over the East. The pattern will allow for an increase in precipitation coverage across the Central U.S. for mid to late week, while shifting well above normal temperatures from the Plains/Mississippi Valley into the East. ...Guidance/Predictability Assessment... Model guidance is reasonably agreeable with the large scale pattern over the lower 48 next week, but plenty of uncertainty in the details which impact surface reflections/frontal timing and placement and sensible weather. The first primary model diagnostics issue is the southern stream trough/possible closed low timing as it enters southern California/northern Mexico late Tuesday or Wednesday and tracks east. With both the 00/06Z and the new 12Z model cycle, the ECMWF and GFS along with the EC-AIFS and AI-GFS were pretty agreeable in showing a slower track than the UKMET and CMC. Thus will lean toward the former cluster with an ECMWF/GFS blend, and this maintains good continuity with the previous WPC forecast. After this, models agree that additional strong vorticity will drop into the Northwest mid to late week, acting to deepen troughing over the western and central U.S., but with plenty of uncertainty in the details of individual shortwaves embedded within the larger trough. This impacts the resulting surface low track (and thus winter probabilities). One trend in today's models is that the surface low trended notably slower as it moves across the Midwest Friday-Saturday, but still with ample uncertainty in the track and timing. One cause of the uncertainty is possible additional upper energy dropping south from Canada late week. The 12Z ECMWF and AIFS have this vorticity digging into the Northwest while the 12Z GFS/AI-GFS and CMC show it more into the Plains. As the period progressed, the WPC forecast blended increasing proportions of the GEFS and EC ensemble means to mitigate these differences and will continue to monitor. ...Weather/Hazards Highlights... A clipper system moving across the Midwest to Great Lakes and Northeast Tuesday into Wednesday will spread some precipitation there, including possible light freezing rain and light to moderate snow in some areas. Meanwhile, energy dropping south and developing an eastern Pacific/California upper low will continue to bring some generally light precipitation to an already very soggy southern California. Precipitation should be light enough and moving quickly so no flooding threat is anticipated on Tuesday. Additionally, northern stream energy dropping into the Northwest will bring moderate to heavy precipitation to that region on Tuesday and Wednesday. Coastal Washington and Oregon could be at risk of locally heavy rain as a weak atmospheric river pushes through on Tuesday, but the quick movement and dry antecedent conditions should limit the flooding threat there. Meanwhile the Cascades can expect heavy snow. As the southern stream system moves eastward into Wednesday, it will spread precipitation across the Southwest. Though moisture anomalies are well above normal, the lack of instability and progressive nature of this system precludes the need for any excessive rainfall risk in the Day 5/Wednesday ERO. The broad trough in the West will also provide support for moderate snow across mountain areas. As the shortwave and the larger scale trough phase late Wednesday into Thursday, the combined trough should tap into Gulf moisture, leading to rain chances expanding across the south-central Plains and Mississippi Valley Wednesday night and pressing east into the Midwest and Ohio/Tennessee Valleys Thursday- Friday. Wintry precipitation remains possible on the western and northern sides of the precipitation shield in the northern/central Plains to Midwest, but this will be highly depending on the uncertain track and timing of the surface low pressure system. Temperatures are likely to be well above average across the entirety of the country east of the Rockies by midweek. Temperature anomalies of 15 to 30 degrees above average Tuesday to Thursday will be common across the central U.S. and into the Midwest and some daily records for warm lows and highs could be set. Unseasonably warm temperatures will gradually expand and spread eastward later in the week. Meanwhile the West/Southwest should trend colder next week as the pattern turns more amplified and troughing develops, and temperatures are likely to moderate back to normal into the Plains by Friday and Mississippi Valley Saturday as this trough moves east. Tate/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 $$