US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 355 PM EST Tue Jan 12 2021 Valid Friday January 15 2021 - Tuesday January 19 2021 Hazards: - Flooding occurring or imminent across portions of the Southeast, the Mid-Atlantic, and the Pacific Northwest. - Flooding likely across portions of the Pacific Northwest and the Northern Great Basin. - High winds across portions of the Northern/Central Plains, Fri, Jan 15. - Heavy precipitation across portions of the Northeast, Fri-Sat, Jan 15-Jan 16. - Much above normal temperatures across portions of the Northeast, Fri-Sat, Jan 15-Jan 16. - Heavy rain across portions of the Lower Mississippi Valley and the Southern Plains, Tue, Jan 19. - High winds across portions of mainland Alaska, Fri, Jan 15. - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Fri-Tue, Jan 15-Jan 19. Detailed Summary: Throughout the medium range period (Friday, January 15 - Tuesday, January 19) a deep upper-level low will fuel much of the activity East of the Rockies, while a persistent ridging pattern will keep the West relatively quiet. Following the eastern progression of the upper-level low, a low pressure/frontal system at the surface will descend over the Upper Great Lakes from southern Canada on Thursday, bringing heavy snow to the region. While most of the heavy snow is forecast to fall just prior to the period some lingering snowfall is expected on Friday, the heaviest of which will be isolated to the southern coast of Lake Superior. Behind the frontal system, a strong pressure gradient positioned over the Northern and Central Great Plains may generate high winds across the region that have the potential to be hazardous. As the surface low and its associated fronts continue tracking eastward, a mix of rain and snow is forecast to impact the Northeast Friday through Saturday. The latest guidance suggests heavy rain is likely to fall in warmer areas closer to the coast, while snow is expected to be the main form of precipitation at locations inland and in northern New York, where there is increased potential for heavy lake effect snow downwind of Lake Ontario. However, no definitive determination of precipitation type can be made at this time, therefore the whole region will be marked as at risk for heavy precipitation. In the beginning of next week a new low pressure/frontal system will emerge in southern Texas and move offshore into the Gulf of Mexico, where it will remain stationary into Tuesday. Onshore moisture transport associated with this system will bring heavy rain to the Gulf Coast. While deterministic models currently do not agree on the exact placement of this heavy rain, ensemble means place it somewhere along the eastern Texas and western Louisiana coastlines where soil saturation is high, enhancing the potential for rain-induced flooding. Above normal temperature anomalies for both maximum and minimum temperatures will be present all around the CONUS throughout the period. These will be non-hazardous in the Northern Tier, where temperatures will reach above freezing with minimal snow cover, and the Desert Southwest, where some daily record highs may be tied or broken on Friday. In the New England interior maximum temperature anomalies between 12 and 15 degrees above average are forecast, which will bring daily temperatures above freezing, thereby serving to melt part of the moderate snow pack already in place. Though non-hazardous on its own, the excess runoff associated with this snowmelt combined with a heavy precipitation event and above average streamflow may cause flooding along streams and rivers. In Alaska, a tight pressure gradient is forecast to develop over the Northern Mainland between a deep low in the Gulf of Alaska and a strong high in the Arctic Ocean on Friday, producing high winds over and around the Lisburne Peninsula. Additionally, a series of frontal systems are forecast to move through the Gulf of Alaska during the period, bringing a virtually constant string of heavy rain to the coast from the Southcentral region through the Alaska Panhandle. While these systems may generate high winds and significant waves, these hazards are expected to remain mainly offshore. Zavadoff