Extended Forecast Discussion NWS Weather Prediction Center College Park MD 152 PM EST Wed Jan 05 2022 Valid 12Z Sat Jan 08 2022 - 12Z Wed Jan 12 2022 ...General Pattern Overview... An amplified but progressive upper level pattern should prevail into the start of next week with a deep trough tracking from the Rockies to the East Coast and a ridge axis moving into the western U.S. from the eastern Pacific. By early-mid week the pattern should transition somewhat as eastern Pacific shortwave energy splits around the western U.S. ridge--leading to a possible southern stream trough reaching the southwestern U.S. and far northwestern Mexico--and a flatter trend to the mean flow across the eastern half of the country. The main precipitation event during the period will be an area of locally moderate to heavy rainfall over parts of the South/Tennessee Valley this weekend, aided by moist flow ahead of a cold front. Another surge of cold air will spread across the northern Plains through the Upper Midwest Sunday into the first part of next week, followed by a warmer trend over the central U.S. ...Guidance/Predictability Assessment... Guidance continues to be well-behaved in terms of agreement and continuity for about the first half of the period when the Pacific into western U.S. upper ridge and downstream trough are dominant and large-scale features. Likewise forecasts for the cold front ahead of the upper trough are fairly consistent. A blend of 00Z/06Z operational models reflected consensus well for this part of the forecast. Then models and ensemble members continue to vary for specifics of how eastern Pacific shortwave energy may split as it nears the West Coast. These differences ultimately affect flow over/near the Southwest as well as locations east of the Rockies, with northern stream flow determined in part by how Pacific energy goes around the western U.S. ridge and southern tier flow influenced by the pattern to the west. For this more uncertain part of the forecast, transitioning to a blend of models and GEFS/ECMWF means helped to keep the overall evolution fairly stable with only modest refinements in detail. ...Hazards/Sensible Weather Highlights... Gulf moisture advecting northward ahead of a developing Plains/Midwest cold front will support increasing coverage of showers and thunderstorms from eastern Texas and the central Gulf Coast to the Ohio Valley and Mid-Atlantic region this weekend, with lighter rainfall expected farther north. There will likely be some embedded heavier rainfall across portions of the Deep South where convection is persistent. Areas from the upper Great Lakes to the Northeast could see wintry weather, with the best snowfall prospects over northern New England and northern New York. Freezing rain and/or sleet may be among the hazards over and near parts of the northern half of the Appalachians for a time as moisture overruns cold air at the surface. Parts of the Great Lakes may see lake effect snow behind the passing front. Dry conditions will likely prevail over a majority of the lower 48 during the first half of next week. Exceptions include some showers and mountain snow over western Washington and Oregon as one or more systems brush the region and some precipitation spreading into the Southwest and southern Plains. Precipitation amounts will be sensitive to the exact details of the upper trough approaching/reaching the Southwest. On Saturday the Plains/Midwest will see some moderation of the severe cold before the next arctic surge reaches into the northern tier states by Sunday into Tuesday morning. The second surge may not be quite as intense as what is expected for the end of this week, but temperatures could still be 10-25F below normal from eastern Montana to Wisconsin. The cold air will eventually reach the East Coast as well, bringing highs down to 10-25F below normal from the Mid-Atlantic through New England on Tuesday. From Saturday into Sunday above normal temperatures will progress from the southern Plains to the Deep South and Southeast U.S. Greatest anomalies should be for overnight lows 15-25 degrees above normal across the central Gulf Coast region Sunday morning. The northern-central Plains will trend warmer next week, reaching 10-15F or so above normal over some locations by Tuesday-Wednesday. Seasonably cold conditions are likely west of the Continental Divide with readings generally within 10 degrees of climatological averages. Rausch/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, winter weather outlook probabilities and heat indices are at: 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/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml