Extended Forecast Discussion NWS Weather Prediction Center College Park MD 321 PM EST Thu Jan 06 2022 Valid 12Z Sun Jan 09 2022 - 12Z Thu Jan 13 2022 ...General Pattern Overview... An amplified upper flow regime will prevail from the weekend into early next week with a ridge over parts of the western U.S. north into Canada and a deep upper trough crossing the eastern half of the country. Guidance has been suggesting that a developing split flow pattern from the eastern Pacific into the West will decrease predictability of forecast details--including leading energy that may reach over or near the Southwest in the form of a trough/embedded low, upstream Pacific energy, and northern stream impulses carried along into cyclonic flow that may linger over the eastern U.S. ...Guidance/Predictability Assessment... For the most part guidance has remained consistent and agreeable with the deep upper trough crossing the East along with the leading cold front expected to clear most of the East Coast by early Sunday. The same is true for the upper ridge building into the West Sunday-Monday. Models and ensembles continue to vary for the specifics of splitting Pacific energy early next week. Latest trends seem to be favoring a moderately south and slow upper low scenario, with this feature still near Baja California into day 6 Wednesday (making Wed's 12Z ECMWF look like an open/fast extreme). The upper low/trough may finally get kicked out by Thursday as additional Pacific energy approaches. However this latter energy has considerable uncertainty with a lot of model/ensemble spread and the overall means showing another ridge building over the West Coast at that time. Guidance also diverges for shortwave details within the progressive northern stream flow from the Pacific, around/through the western U.S./Canada ridge, and east-southeast through Canada and the lower 48. Confidence in any specific solution is minimal. The updated forecast used an operational model blend for the first half of the period and then incorporated some 06Z GEFS/00Z ECMWF mean input. This approach reflected consensus early in the period and then the most common ideas later on while becoming conservative with specifics given the increasing guidance spread. ...Hazards/Sensible Weather Highlights... Rain and thunderstorms likely to be in progress ahead of a Great Lakes to Southern Plains cold front as of early Sunday should continue to spread eastward during the day and into Sunday night. Expect the highest rainfall totals to be over portions of the South/Tennessee Valley/southern Mid-Atlantic, where some heavier activity may be possible. Localized flooding could be within the realm of possibility where the most intense rainfall coincides with areas that have seen well above average precipitation recently. Amounts will be lighter over the northern half of the East. Areas from the upper Great Lakes to the Northeast could see wintry weather, with the best snowfall prospects over Michigan and northern New York as a result of lake effect snow. 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. Elsewhere the main areas of precipitation should be over the Pacific Northwest as one or more systems brush the region as they weaken, and over the Southwest into Southern Plains in association with the upper low/trough currently forecast to be around the Southwest/Baja California into midweek. Coverage and amounts for this latter area will depend on uncertain details for the upper system. The next blast of arctic air will make its presence known across the Northern Plains and Upper Midwest by Sunday in the wake of the strong cold front with temperatures 10-25F below normal. The cold weather will eventually reach the East Coast in modified form by Tuesday, bringing highs down to 10-25F or so below normal from the Mid-Atlantic through New England for one of the coldest days of the season thus far. It should still be rather mild across the South ahead of the front on Sunday followed by a colder trend. The central U.S. will see a pronounced warming trend next week with expanding coverage of max/min temperatures 10-20F above normal Tuesday onward with some locally warmer readings possible on some days. Expect most of the West to see temperatures within 10F on either side of normal through the period. 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 Hazards: - Heavy rain across portions of the Lower Mississippi Valley and the Southern Plains, Wed-Thu, Jan 12-Jan 13. - Heavy rain across portions of the Southeast, the Lower Mississippi Valley, the Southern Appalachians, the Ohio Valley, and the Tennessee Valley, Sun, Jan 9. - Heavy snow across portions of the Northeast and the Great Lakes, Sun-Mon, Jan 9-Jan 10. - Freezing rain across portions of the Great Lakes, the Mid-Atlantic, the Northeast, the Central Appalachians, and the Ohio Valley, Sun, Jan 9. - Much below normal temperatures across portions of the Northern Plains and the Northern Rockies, Sun, Jan 9. - Much below normal temperatures across portions of the Middle Mississippi Valley, the Great Lakes, the Upper Mississippi Valley, and the Northern Plains, Sun-Tue, Jan 9-Jan 11. - Much below normal temperatures across portions of the Middle Mississippi Valley, the Great Lakes, and the Upper Mississippi Valley, Mon-Tue, Jan 10-Jan 11. - Much below normal temperatures across portions of the Mid-Atlantic, the Northeast, and the Great Lakes, Tue-Wed, Jan 11-Jan 12. - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Sun-Tue, Jan 9-Jan 11 and Thu, Jan 13. - Heavy precipitation across portions of mainland Alaska, Sun, Jan 9. - High winds across portions of the Alaska Panhandle and mainland Alaska, Sun, Jan 9. - Much below normal temperatures across portions of mainland Alaska, Sun, Jan 9. 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