US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 246 PM EST Wed Jan 08 2020 Valid Saturday January 11 2020 - Wednesday January 15 2020 Hazards: - Heavy precipitation across portions of the Pacific Northwest and northern California, Sat-Mon, Jan 11-Jan 13 and Wed, Jan 15. - Heavy precipitation across portions of the Midwest, Lower Great Lakes, and the Northeast, Sat-Sun, Jan 11-Jan 12. - Heavy rain across portions of the Lower Mississippi Valley, the Southeast, and the Tennessee Valley, Sun-Tue, Jan 12-Jan 14. - Heavy rain across portions of the Tennessee Valley and the Lower Ohio Valley, Wed, Jan 15. - Heavy rain across portions of the Ohio Valley, the Tennessee Valley, and the Gulf Coast, Sat, Jan 11. - Heavy snow across portions of New England and the Northern Rockies, Sat-Sun, Jan 11-Jan 12. - Heavy snow across portions of the Upper Great Lakes, Sat, Jan 11. - Severe weather across portions of the Gulf Coast and Tennessee Valley, Sat, Jan 11. - Flooding Lower and Middle Mississippi Valley into the Ohio Valley. - Flooding occurring or imminent across portions of the Lower Mississippi Valley, the Pacific Northwest, and the Northern Plains. - Much below normal temperatures across portions of the Northern Plains and the Northern Rockies, Mon-Wed, Jan 13-Jan 15. - High significant wave heights for coastal portions of the Pacific Northwest, Sat, Jan 11. - Much below normal temperatures across portions of mainland Alaska, Sat-Sun, Jan 11-Jan 12. - Much below normal temperatures across portions of the Alaska Panhandle, Sat-Tue, Jan 11-Jan 14. Detailed Summary: The weather pattern will remain quite active through this Day 3-7 period, with a couple of waves of heavy precipitation expected over parts of the central and eastern U.S. along with the Pacific Northwest, while arctic air settles into the Northern Plains/Rockies. Heavy rainfall from the central Gulf Coast to the Ohio Valley will be ongoing from the short range period this weekend as significant Gulf of Mexico moisture interacts with a frontal boundary shifting into the eastern third of the country. Along the northern edge of the precipitation shield, heavy snowfall is possible across portions of the Great Lakes on Saturday and eventually northern Maine by Sunday. In between, there remains question on precipitation type or more likely a possible changeover from rain to sleet/freezing rain or eventually snow from portions of the mid-Mississippi Valley to the interior Northeast. This area may become more refined in the coming days as the forecast becomes more clear. By the end of the weekend, the trailing edge of the frontal boundary should lift northward as a warm front into the Gulf Coast states. Another round of heavy precipitation should focus along the front Sunday-Monday, the heaviest axis of which should be south of the first round this weekend. Another upper level system moving into the Central U.S. during the middle of next week should draw more moisture up from the Gulf of Mexico to bring another area of heavy rainfall to portions of the Middle Mississippi Valley, Tennessee Valley, and lower Ohio Valley next Wednesday. There is some lingering uncertainty on the exact axis and amounts with this third event, though there is at least a good signal for heavy rainfall somewhere in this general area. Note that some areas may see overlap between multiple heavy rainfall episodes, especially the Tennessee Valley, which would increase flooding and flash flooding concerns. Meanwhile out West, a potent low and associated frontal system approaching the coast this weekend will spread heavy mountain snow and coastal/valley rain into much of western Washington and Oregon and into northern California. This system will also bring gusty winds and the potential for significant waves through Saturday along the coast. Onshore flow will maintain the threat for continuing precipitation through the weekend into early next week, but given lower moisture content behind the main front Friday, predicted amounts are not expected to be excessive. Over the northern Intermountain region, the main slug of moisture associated with the front will bring marginally heavy snows to some of the higher elevations through Saturday. Yet another low pressure system looks to approach the coast around the middle of next week which could bring a second round of heavy precipitation to parts of the Pacific Northwest next Wednesday. In between over the north-central U.S. and the Rockies, a very cold arctic air mass will gradually be settling southward over the region. Temperatures are expected to average up to 20-25 degrees below normal across Montana Sunday; this cold air will spread southeastward into the Dakotas early next week. High temperatures across this region may struggle to get above 0F. Across Alaska, much below normal temperatures are forecast to continue across east-central portions of the mainland through the weekend. Much of the Panhandle will also experience colder than average temperatures for much of the Day 3-7 period as the arctic air spills over the Canadian Rockies. Santorelli