US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 239 PM EST Tue Jan 07 2020 Valid Friday January 10 2020 - Tuesday January 14 2020 Hazards: - Heavy precipitation across portions of the Pacific Northwest and the Northern Great Basin, Fri, Jan 10. - Heavy precipitation across portions of the Central Plains, the Lower Mississippi Valley, the Great Lakes, the Middle Mississippi Valley, the Northeast, the Upper Mississippi Valley, the Southern Plains, and the Ohio Valley, Fri-Sun, Jan 10-Jan 12. - Heavy rain across portions of the Central Plains, the Mid-Atlantic, the Lower Mississippi Valley, the Central Appalachians, the Tennessee Valley, the Great Lakes, the Middle Mississippi Valley, the Northeast, the Southern Appalachians, the Southeast, the Southern Plains, and the Ohio Valley, Fri-Sat, Jan 10-Jan 11. - Heavy rain across portions of the Lower Mississippi Valley, the Tennessee Valley, the Mid-Atlantic, the Southern Appalachians, the Southeast, the Southern Plains, and the Ohio Valley, Mon-Tue, Jan 13-Jan 14. - Heavy snow across portions of the Northern Rockies and the Northern Great Basin, Fri-Sat, Jan 10-Jan 11. - Severe weather across portions of the Lower Mississippi Valley and the Southern Plains, Fri, Jan 10. - Severe weather across portions of the Southeast, the Lower Mississippi Valley, the Southern Appalachians, the Ohio Valley, and the Tennessee Valley, Sat, Jan 11. - Flooding possible across portions of the Middle Mississippi Valley, the Lower Mississippi Valley, the Ohio Valley, and the Tennessee Valley. - Flooding occurring or imminent across portions of the Lower Mississippi Valley, the Pacific Northwest, the Northern Plains, and the Northern Great Basin. - Flooding likely across portions of the Pacific Northwest. - Much below normal temperatures across portions of the Northern Plains and the Northern Rockies, Sun-Tue, Jan 12-Jan 14. - High significant wave heights for coastal portions of the Pacific Northwest, Sat, Jan 11. - Much below normal temperatures across portions of mainland Alaska, Fri-Sun, Jan 10-Jan 12. - Much below normal temperatures across portions of the Alaska Panhandle, Fri-Mon, Jan 10-Jan 13. 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. while arctic air settles into the Northern Plains/Rockies. At the start of the period on Friday, a strong frontal system extending from the Great Lakes to the southern Plains will separate a very warm (in some areas record-breaking), moist air mass to its east from arctic air centered over the Upper Midwest and northern/central Plains. This anomalously moist pre-frontal air will combine with a low pressure riding along the front to support widespread heavy precipitation from the southern Plains into the Ohio Valley on Friday. The majority of the precipitation on Friday will be rain (except the far northern/western periphery of the system), with upwards of 2-4 inches possible from northeastern Texas across the mid-Mississippi Valley, along with a threat for severe weather. From Saturday to Sunday, a potent low along the front will track quickly across the Midwest and northeastern U.S. This will allow the front and its heavy rainfall/severe weather to shift into the southeastern states on Saturday, while additional precipitation spreads northeastward through New England. The strong low will also pull in enough arctic air from its north and west to change rain over to snow across sections of the mid-Mississippi Valley, Midwest and Great Lakes states on Saturday. While the system will be moving quickly, there is still a threat for moderate to locally heavy accumulations. In the cold sector northeast of the main surface low, arctic air filtering southward out of southern Canada may result in a swath of locally heavy freezing rain/sleet across parts of the northeast Saturday evening through Sunday. It's a little too early to have confidence in the exact placement of this area of mixed precipitation, but it will be something to monitor through the rest of this week. There will likely be a brief respite from significant precipitation in the east on Sunday into early Monday, but moisture will again get drawn northward ahead of a developing frontal low and bring another round of heavy rainfall to sections of the southeast. Indications currently suggest that the axis of heaviest rain (around 1-3 inches Monday-Tuesday) will mostly be farther to the south and east of the precipitation that falls this coming weekend. However, the model guidance is not in good agreement with this feature, so confidence is relatively low in both its placement and the magnitude of expected rainfall. In the Pacific Northwest, a potent low and associated frontal system approaching the coast Friday will spread heavy mountain snow and coastal/valley rain into Washington and Oregon (mainly Cascades westward). This feature will also bring gusty winds and the potential for significant waves late Friday-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 of Idaho and eastern Oregon Friday evening into early Saturday. Over the north-central U.S. and 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 will struggle to reach 0. 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. Klein