US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 257 PM EST Tue Feb 11 2020 Valid Friday February 14 2020 - Tuesday February 18 2020 Hazards: - Heavy precipitation across portions of the Pacific Northwest and the Northern Great Basin, Sat-Sun, Feb 15-Feb 16. - Heavy rain across portions of the Lower Mississippi Valley, the Tennessee Valley, the Middle Mississippi Valley, the Southern Appalachians, the Southern Plains, and the Ohio Valley, Mon-Tue, Feb 17-Feb 18. - Heavy snow across portions of the Northern Rockies and the Northern Great Basin, Sat-Sun, Feb 15-Feb 16. - Heavy snow across portions of the Central Rockies, the Central Great Basin, the Northern Rockies, and the Northern Great Basin, Sun, Feb 16. - Heavy snow across portions of the Great Lakes and the Upper Mississippi Valley, Mon, Feb 17. - Flooding possible across portions of the Lower Mississippi Valley, the Central Appalachians, the Tennessee Valley, the Southern Appalachians, the Southeast, the Southern Plains, and the Ohio Valley. - Flooding occurring or imminent across portions of the Lower Mississippi Valley, the Tennessee Valley, the Middle Mississippi Valley, the Mid-Atlantic, the Southeast, the Pacific Northwest, and the Ohio Valley. - Flooding likely across portions of the Southeast, the Mid-Atlantic, and the Pacific Northwest. - Much below normal temperatures across portions of the Middle Mississippi Valley, the Great Lakes, the Upper Mississippi Valley, the Northern Plains, and the Ohio Valley, Fri, Feb 14. - Much below normal temperatures across portions of the Northeast and the Great Lakes, Fri-Sat, Feb 14-Feb 15. - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Mon-Tue, Feb 17-Feb 18. - Much below normal temperatures across portions of mainland Alaska, Fri-Mon, Feb 14-Feb 17. Detailed Summary: Over the CONUS, the main concern at the start of this medium range period (Friday, Feb 14) will be much below normal temperatures stretching from the Upper Mississippi Valley into New England thanks to a strong arctic air mass settling over the region. Temperatures will average 15-20 degrees below normal, resulting in highs mostly in the single digits and teens with lows well below zero. The cold air will quickly retreat from the Upper Mississippi Valley and Great Lakes region by the start of the weekend, but hang on through Saturday across northern New England. On Saturday, a potent short wave trough and associated area of low pressure will move into the Pacific Northwest. The models continue to indicate that this feature will tap into a feed of subtropical Pacific moisture and thus is likely to bring a period of heavy precipitation to western Washington and Oregon (rain at the coast an in valleys...snow at the higher elevations). Local amounts of 2-3 inches are likely in favored upslope regions. The system is expected to amplify somewhat as it translates inland during Sunday, and while the amount of moisture available will be less (most will be trapped by the Cascades), there should be enough lifting to produce moderate to heavy snowfall to sections of northeastern Oregon and the higher terrain in northern/central Idaho. The heaviest precipitation over this region is likely to fall from Saturday evening through Sunday morning, with accumulations of a foot or more possible over some of the highest elevations. Have a little more confidence than yesterday extending the heavy snow potential into portions of western Wyoming, eastern Idaho and north-central Utah during Sunday. As this feature emerges onto the Plains Sunday night into Monday, surface low pressure will develop and begin to draw Gulf of Mexico moisture northward across the central U.S. A swath of moderate to locally heavy snowfall may break out over the western Great Lakes region as this low transits through the Upper Mississippi Valley during Monday. At the moment, it appears that the system will progress relatively quickly across the region, so while we don't expect a widespread major event, some locations across Wisconsin and Michigan could see up to 8-12 inches. The latest guidance is showing a fair amount of disagreement handling this feature, so confidence with the timing and placement of heavy snowfall is low. On Tuesday, snowfall may break out across northern New England as the storm moves eastward; however, there's enough uncertainty to preclude drawing a hazard at this time. Farther south, widespread showers and thundershowers are expected to break out along and ahead of the cold front associated with the abovementioned low. Yesterday, it looked like this activity may break out over the southeast on Sunday. Today, it seems to be holding off a little and possibly focusing farther to the west and north. However, there remain rather large differences among the models, so confidence remains quite low with the placement and timing of this hazard area. We'll continue to monitor this closely as portions of the Southeast have received copious rainfall over the past month, so soils are already quite saturated and additional rainfall may result in localized flooding. Across Alaska, below to much below normal temperatures are expected through the period across much of the central and northern part of the mainland as an Arctic air mass remains well-entrenched. There are indications that temperatures will moderate over the eastern part of the mainland early next week as a strong storm moves through the Gulf of Alaska and draws milder air northward. This storm also is expected to bring the potential for heavy rain and snow, mostly across the south-central/southeastern mainland and northern Panhandle Monday before shifting southward across the entire Panhandle Tuesday. Northerly flow behind this feature may allow the much below normal air that's over the central/northern mainland to sink southward and cover all of western Alaska and the eastern Aleutians by Monday-Tuesday. Klein