Extended Forecast Discussion NWS Weather Prediction Center College Park MD 207 AM EST Thu Jan 9 2025 Valid 12Z Sun Jan 12 2025 - 12Z Thu Jan 16 2025 ... Arctic airmass to reinforce over the lower 48 next week... ...Pattern Overview and Guidance/Predictability Assessment... An amplified mean upper trough with a series of embedded shortwaves will settle over much of the lower 48 by early next week in a cold winter pattern. Amplified upper ridging slowly working from the eastern Pacific to the Northwest/West will coincide with downstream shortwave digging through a cooling West, likely leading to the splitting and undercutting of developing closed low energy back over the Southwest to offshore California. Meanwhile, high pressure building in the West early next week and increased pressure gradients may suggest stronger than guidance winds/gusts. Forecast spread and uncertainty seem below normal in guidance Sunday into Tuesday in a less active weather pattern for much of the lower 48. Predictability seems to lower toward average levels into mid-later next week, especially over the more transitional flow over the West and eastern Pacific. The WPC medium range product suite was primarily derived from a blend of best clustered guidance from the 18 UTC GFS/GEFS mean, the 12 UTC ECMWF and the 12 UTC ECMWF/Canadian ensemble means along with the compatible 01 UTC National Blend of Models. WPC blend emphasis on the models through early next week moves to the ensemble means mid-later next week amid slowly frowing variances. This forecast plan maintains good WPC continuity and seems mainly in line with latest 00 UTC models. ...Weather/Hazards Highlights... An anomalously cold air mass will remain in place over the South, Southeast, and Mid-Atlantic through the weekend, and trailing fronts may continue to focus periodic rain/convection back across Florida, the Gulf of Mexico, and southern Texas next week. Low pressure system translation and upper support should favor light to moderate organized snows expected to slowly work over the Midwest and Great Lakes early next week, then leading to the triggering of additional lake effect snows. In the wake of this system, another blast of Arctic air is forecast to spill into the north-central U.S. and spread to the East and Southeast next week. Hazardous cold temperatures are expected from the northern Plains to the Gulf and Southeast Coasts, with temperature anomalies potentially reaching 10-20 degrees below normal. 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