US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 235 PM EST Mon Feb 01 2021 Valid Thursday February 04 2021 - Monday February 08 2021 Hazards: - Heavy snow across portions of the Great Lakes and the Upper Mississippi Valley, Thu-Fri, Feb 4-Feb 5. - Much below normal temperatures across portions of the Central Plains, the Lower Mississippi Valley, the Central Appalachians, the Tennessee Valley, the Great Lakes, the Middle Mississippi Valley, the Southern Appalachians, the Upper Mississippi Valley, the Southeast, the Southern Plains, and the Ohio Valley, Sun-Mon, Feb 7-Feb 8. - Much below normal temperatures across portions of the Lower Mississippi Valley, the Central Appalachians, the Tennessee Valley, the Great Lakes, the Mid-Atlantic, the Southern Appalachians, the Southeast, the Southern Plains, and the Ohio Valley, Mon, Feb 8. - Much below normal temperatures across portions of the Central Plains, the Upper Mississippi Valley, the Middle Mississippi Valley, the Northern Plains, and the Northern Rockies, Sat-Mon, Feb 6-Feb 8. - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Fri-Sat, Feb 5-Feb 6. Detailed Summary: The medium range period (Thursday, February 4th to Monday, February 8th) will feature a few strong cold fronts traversing the central and eastern United States. The leading cold front on Thursday and Friday will be associated with a strengthening low pressure system near the Great Lakes. As a result, heavy snow will likely develop on the northwest side of the low and impact areas across the Upper Midwest and Great Lakes. Snowfall amounts over 6 inches will be possible and could lead to travel disruptions across the area. Further south, rain showers and isolated thunderstorms will accompany the system across the Tennessee Valley and Southeast between Thursday and Saturday. Instances of heavy rain may impact the southern Appalachians on Friday, but forecast rainfall amounts have decreased and therefore a hazard area was not added to the chart today. The most widespread hazard during this time frame will be associated with a secondary cold front that will bring the coldest arctic air of the season for most. Subzero degree temperatures are forecast to enter the northern Plains behind the front on Friday and spill into the central Plains by Saturday. Low temperatures around 10 to 20 degrees below average will then enter the Ohio Valley by Sunday and Monday. Cold air will also be found as far south as the Southern Plains, central Gulf Coast, and Southeast by Monday. Places such as Chicago and Minneapolis will likely experience multiple days with low temperatures below zero beginning on Saturday. Wind chill values will be even colder and possibly in the minus 20 degree range. Confidence is fairly high regarding the cold air surge into the central U.S., but a potential wrinkle in the forecast is a possible storm system along the East Coast Sunday into Monday. Most forecast guidance has trended stronger and faster with the upper-level trough and leading aforementioned cold front. This has then led to a scenario where a developing surface wave gets pushed out to sea and produces only light-to moderate snow across New England. However, there is the potential that guidance is underestimating the ridging across the eastern Atlantic and this would allow for energy dropping out of central Canada to round the trough axis and develop a stronger system that moves along the East Coast. For right now, confidence is not high enough to add any hazards along the East between Sunday and Monday. Current probabilities for impactful snow remain between 10-30% from the southern Appalachians to Northeast, with slightly higher probabilities in New England. Given this potential system is 6 to 7 days out, a lot of scenarios are still on the table and changes to the forecast are possible over the next few days. For Alaska, a weak atmospheric river will impact the south-central coast on Friday and Saturday. Up to 2 inches of rain will be possible along the lower elevations, with heavy snow across the higher terrain. For interior and northern portions of the state, below average temperatures and gusty winds could make for dangerously cold wind chills Thursday and Friday. However, temperatures were not quite cold enough to meet hazardous threshold during today's forecast. A reevaluation may be needed tomorrow. Snell