Extended Forecast Discussion NWS Weather Prediction Center College Park MD 148 AM EST Sat Jan 4 2025 Valid 12Z Tue Jan 07 2025 - 12Z Sat Jan 11 2025 ...Arctic blast holds central/eastern U.S. grip next week... ...Overview... The weather pattern for next week across much of the nation will quiet down in terms of precipitation aside from periodic Great Lake effect snow enhancement with reinforcement of widespread Arctic flow and some areas of mainly light precipitation in the western and central U.S., but much colder than average temperatures will persist in most areas from the Rockies eastward. There is also an uncertain signal for extent of far south-central U.S. rain/winter precipitation development into later next week to monitor. ...Guidance/Predictability Assessment... Guidance forecast spread and uncertainty overall seem less of an issue than normal well into med-range time scales, including for the latest 00 UTC cycle. A composite of best clustered GFS/ECMWF model and ensemble solutions along with the National Blend of Models (NBM) for the most part seems to provide a consistent and reasonable forecast basis. This solution maintains great WPC product continuity and remains best in line with machine learning guidance. Alternately, less supported but still plausible recent Canadian runs have been the least aligned with this composite with development of a less amplified/more progressive southern stream and a more amplified/less progressive northern stream in split flow as systems dig to the lee of full latitude upper ridging built along/off the west coast of North America. ...Weather/Hazards Highlights... Great lake effect snows will be periodically rejuvenated with deep cold surges next week given ample flow amplitude. The NBM runs remain characteristically underdone with this potential, leading to manual corrective adjustments. Light to modest precipitation including elevation snow will spread focus down through the Rockies next week, and eventually the north-central U.S. with an emerging surface system. Farther south, there are some chances for precipitation from the Southwest to Southern Plains and Lower Mississippi Valley and vicinity dependent on uncertain timing/ejection of energies in a separated southern stream. An emerging precipitation pattern may unfold into later next week, and with cold air in place from Texas eastward, some areas may need to monitor any onset of wintry precipitation. Colder than normal temperatures are likely across the central and eastern U.S. underneath rounds of upper troughing and with cold surface high pressure systems. Notable cold is possible in the far northern tier, with high temperatures barely reaching 0F and lows between -10F and -15F in some areas. This should not be record breaking, but the cold could still be hazardous as wind chill values may dip below -20F to -30F. Temperature anomalies of 10-20 degrees below normal are also likely from the central Plains and Mid-Mississippi/Ohio Valleys through the Appalachians next week, especially as temperatures hold down in snow covered areas from a major lead short range winter storm. Meanwhile, upper ridging in the western U.S. will offer slightly above normal temperatures. Schichtel 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