US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 255 PM EST Tue Dec 29 2020 Valid Friday January 01 2021 - Tuesday January 05 2021 Hazards: - Heavy precipitation across portions of the Pacific Northwest and the Northern Great Basin, Fri-Sun, Jan 1-Jan 3. - Heavy precipitation across portions of California, the Central Great Basin, the Pacific Northwest, the Northern Great Basin, and the Southwest, Mon-Tue, Jan 4-Jan 5. - Heavy precipitation across portions of the Northeast, the Central Appalachians, the Middle Mississippi Valley, the Mid-Atlantic, the Upper Mississippi Valley, the Great Lakes, and the Ohio Valley, Fri, Jan 1. - Heavy rain across portions of the Southeast, the Mid-Atlantic, and the Southern Appalachians, Fri-Sat, Jan 1-Jan 2. - Heavy rain across portions of the Mid-Atlantic and the Northeast, Fri, Jan 1. - Heavy snow across portions of the Northern Rockies and the Northern Great Basin, Sat-Sun, Jan 2-Jan 3. - Heavy snow across portions of the Northern Great Basin, Sun-Mon, Jan 3-Jan 4. - Heavy snow across portions of the Northern Rockies, Sun, Jan 3. - Heavy snow across portions of the Central Plains, the Middle Mississippi Valley, the Great Lakes, and the Upper Mississippi Valley, Fri, Jan 1. - Heavy snow across portions of the Northeast, Sat, Jan 2. - Severe weather across portions of the Southeast and the Mid-Atlantic, Fri, Jan 1. - Flooding possible across portions of the Middle Mississippi Valley and the Ohio Valley. - Heavy precipitation across portions of the Alaska Panhandle, Fri-Sat, Jan 1-Jan 2. - High winds across portions of the Aleutians, Fri, Jan 1. - High significant wave heights for coastal portions of the Aleutians, Fri, Jan 1. Detailed Summary: A pretty active weather pattern will usher in the New Year for much of the eastern half of the country and the Pacific Northwest. Starting in the east, a storm system will track from the south-central Plains into the upper Midwest during Friday, then push into New England on Saturday. To the west of the storm track, a narrow band of moderate to heavy snow is possible, with the current guidance suggesting that it extends from northeastern Kansas across southern Iowa and Wisconsin, and northern sections of the lower peninsula of Michigan. Precipitation may be mixed with sleet and freezing rain at times over parts of this region, which would limit the total accumulations. Farther east through the lower Great Lakes, Mid-Atlantic states and southern New England, Friday will feature a period of mixed precipitation at the start of the event, but changing over to rain as warmer air from the south infiltrates. Cold-air damming may prolong the period of freezing rain/sleet over central/eastern Pennsylvania into New York and southern New England. At this time, a cool rain is expected over the major metro areas of Philadelphia and New York City. Along the trailing cold front, heavy rainfall and the potential for severe weather exists over the southeast, mainly across South Carolina, Georgia, and the Florida Panhandle on Friday. On Saturday as the low shifts into New England, thereâ€s a chance for heavy snow across the northern half of Maine as the cold air remains locked in place. The trailing cold front will remain active with showers and thundershowers possible over the eastern Carolinas, southeast Georgia, and the northern Florida Peninsula. One area of high uncertainty is the degree that low pressure develops along this front later Saturday-Sunday. Several models show a fairly well-defined low moving through the Mid-Atlantic states early Sunday, then strengthening off the east coast as it tracks up along the southern New England coast. If this scenario were to play out, the potential exists for an area of moderate to heavy snowfall over sections of eastern New York into southern New England late weekend into early next week. The other region of unsettled weather in the lower 48 will be across the Pacific Northwest, northern California, and the northern Intermountain region. A parade of storm systems will impact the region with heavy coastal/valley rainfall and snow at the higher elevations. On Friday, a front will cross the region, with the heaviest precipitation mostly confined to Washington and Oregon from the Cascades westward. A more substantial system with deeper moisture and stronger onshore flow will move in later Saturday through early Sunday, affecting much of the same area, but with notably higher amounts (locally 2-4â€). This system will also bring moderate to heavy snowfall across the higher elevations in northern and central Idaho and eventually the Tetons in western Wyoming. There will be a relative respite Sunday evening into Monday morning before another front slams onshore. However, expect the heaviest precipitation to spread farther down the west coast into northern/Central California. The models then support potentially yet another storm for Tuesday impacting the Pacific Northwest. Over Alaska, the main story will be the extremely intense cyclone that will track into the north-central Pacific later this week. The primary impacts will be over the western and central Aleutians where high winds and seas will predominate Thursday-Friday. Conditions will improve over the weekend as this low weakens. Farther east, the same series of storm systems impacting the Pacific Northwest will take aim at the southern part of the Panhandle. While precipitation is likely throughout the Day 3-7 period, the front with the deepest moisture is expected to produce the most significant amounts Friday-Saturday. Klein