418 FXUS02 KWBC 020644 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 144 AM EST Fri Jan 2 2026 Valid 12Z Mon Jan 05 2026 - 12Z Fri Jan 09 2026 ...Additional rounds of rain and mountain snow for California early next week... ...Overview... With troughs off both coasts, flow across the CONUS itself should be pretty zonal to start the period on Monday, though with a couple of north-central to northeastern U.S. clipper systems. Troughing off the West Coast may close off into an upper low off California before it moves inland by mid-week. This likely brings additional rounds of possibly heavy rains and mountain snows for California. This shortwave/low should shift inland across the Southwest and eventually the central states as additional energy dives down the West Coast late week. This next wave should allow for a fairly amplified pattern to end the work week, with strong ridging along the East Coast and deeper troughing moving through the West. This brings an increase in precipitation coverage across the Central U.S. for late week, and well above normal temperatures for the East. ...Guidance/Predictability Assessment... Model guidance generally shows good agreement on the large scale pattern, but with significant uncertainty still in the details and timing of individual systems. Beginning of the period for the northern tier should be dominated by shortwaves. There are some timing differences with these, which do impact surface low/frontal placement and temperatures, but it is difficult to pick out outliers in such shallow flow. A multi-model blend should handle this aspect of the forecast. The main forecast concern and source of uncertainty for the medium range will be with troughing off the West Coast on Monday, which shows some increasing agreement may close off an upper low off California. Timing difficulties become evident as early as Tuesday, with the UKMET and ECMWF still on the faster side of the guidance envelope (though the new 00z run did come in slightly slower). The GFS is slower, but the new 00z run tonight did trend faster than the previous run. Prefer a solution for now closest to the ECMWF and CMC, which has support from the AI guidance and the ensemble means. WPC trended quickly towards the ensemble means for the latter half of the period as this system translates inland and troughing becomes reestablished across the West with the next wave. There is a lot of uncertainty in the details with the evolution of this and also how strong the initial shortwave is as it pushes through the Central U.S. and the Midwest. ...Weather/Hazards Highlights... Shortwaves rounding the eastern Pacific/western U.S. trough will provide support for possibly a few rounds of weak to moderate atmospheric rivers and precipitation in the West into next week. With one moisture plume exiting the region at the very end of the short range, the next one should move into California by Monday. Guidance continues to focus mostly on northern to central California for better rainfall potential, but some moderate QPF may make it as far south as the sensitive Transverse Ranges. Thus, continue to show a marginal risk on the Day 4/Monday Excessive Rainfall Outlook from northern California to the Transverse Range. Heavy snow is likely for the higher terrain of the Sierra. More modest precipitation amounts are expected farther north in the Pacific Northwest and farther east into the Intermountain West. Precipitation is forecast to continue into Tuesday across the Southwest, while a northern stream wave leads to increasing Pacific Northwest precipitation as well. Elsewhere across the country, a couple of clipper systems are forecast to track from the Upper Midwest to the Great Lakes and then the Northeast during the period. These relatively weak systems could produce a swath of mainly light snow and perhaps some mixed wintry precipitation along the southern portion of its track. Also by midweek, troughing tracking into the Rockies/High Plains from the West could tap into Gulf moisture and lead to increasing rain chances (and perhaps some thunderstorms) across southern/central parts of the Plains and Mississippi Valley into the Mid-South. Coverage and amounts remain highly uncertain given differences in the larger pattern. Temperatures are likely to be much warmer than average across a wide expanse of the country into much of next week, especially across the Plains, where temperature anomalies of 15 to 30 degrees above average will be common. Daily records for warm lows and highs could be set across the Intermountain West and Plains. Unseasonably warm temperatures will gradually expand and spread eastward through the week, bringing anomalies of +15 to +25 degrees to the Mississippi Valley and eventually +10 anomalies to the East Coast, after a colder than average start to the week across the Northeast. The West/Southwest should remain near or below normal much of the week as the pattern turns more amplified and troughing develops. 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 $$