US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 311 PM EST Wed Feb 12 2020 Valid Saturday February 15 2020 - Wednesday February 19 2020 Hazards: - Heavy precipitation across portions of the Pacific Northwest and the Northern Great Basin, Sat, Feb 15. - Heavy rain across portions of the Middle Mississippi Valley, the Lower Mississippi Valley, the Ohio Valley, and the Tennessee 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 Plains, 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. - Heavy snow across portions of the Northeast and the Great Lakes, Tue, Feb 18. - Flooding possible across portions of the Lower Mississippi Valley, 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, and the Ohio Valley. - Flooding likely across portions of the Southeast, the Mid-Atlantic, the Pacific Northwest, and the Tennessee Valley. - Much below normal temperatures across portions of the Northeast, Sat, Feb 15. - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Tue-Wed, Feb 18-Feb 19. - Heavy snow across portions of mainland Alaska, Sun-Tue, Feb 16-Feb 18. - Much below normal temperatures across portions of mainland Alaska, Sat-Wed, Feb 15-Feb 19. Detailed Summary: Starting over the western CONUS, the majority of any potential hazards will essentially be confined to the start of the forecast period, Feb 15-16. The guidance has been very consistent for several days bringing a short wave trough toward the Pacific Northwest Saturday, with the system amplifying as it moves into the northern Intermountain region/Great Basin Sunday. While the area of low pressure along the associated front has trended a bit weaker, there is still expected to be a feed of deep subtropical Pacific moisture into the Washington/Oregon on Saturday. This will support a period of heavy precipitation (rain at the coast and in valleys...snow at the higher elevations) from Saturday into early Sunday, with the main focus from the Cascades westward. As the system progresses inland later Saturday, moderate to locally heavy snows will break out over the higher elevations of northeastern Oregon into northern/central Idaho. Then on Sunday, the focus will shift into the northern/central Rockies and eastern Great Basin, with the heaviest activity likely across western Wyoming, eastern Idaho, north-central Utah and central/northern Colorado. Total snow accumulations over the depicted hazard areas will range upwards of 12-18 inches Saturday-Sunday. As this system emerges into the Plains on Monday, surface low pressure will develop along a strengthening cold front and track northeastward toward the Ohio Valley Monday night, then likely into New England during Tuesday. This system will tap into Gulf of Mexico moisture as it moves through the region, and the strong lifting associated with the amplifying trough will support an area of moderate to heavy snowfall across Wisconsin and Michigan Monday into Tuesday, with wintry precipitation then moving into New England later Tuesday or Wednesday. The model guidance has had a lot of trouble all week coming together on how quickly this system will develop and move through the central and eastern U.S., and this remains the case today. We've got relatively high confidence that there will be a well-organized low pressure system and that it will be a fast-mover. But we've got low confidence on when the precipitation will impact the aforementioned areas. Regardless, there is a reasonable chance that a moderate to heavy snowfall event will impact the Great Lakes and New England early-mid next week. Farther south, showers and thundershowers will break out across the lower-mid Mississippi Valley, Tennessee Valley and southeastern states along and ahead of the cold front associated with the low moving from the Ohio Valley through New England. We've been concerned that this system would bring another round of heavy precipitation early next week to regions that have saturated soils, but model guidance is starting to back off on the amounts. It appears that both lifting along the front and the amount of Gulf moisture will be less significant, and the front is progressing through the region more quickly. Am still keeping a small area across Arkansas, northern Alabama and Mississippi and western Tennessee, with the heaviest precipitation (locally 1-3 inches) falling during Tuesday. Over New England early in the period, Arctic high pressure will bring one more day of much below normal temperatures on Saturday. Temperatures will return to more normal levels by Sunday. Across Alaska, below to much below normal temperatures are expected through the period across much of the mainland (with the exception of south-central and southeastern Alaska) as Arctic air remains well-entrenched. There are indications that temperatures will at least temporarily moderate over the east-central and northeastern parts of the mainland early next week as a strong Pacific storm moves into the Gulf of Alaska and possibly inland over southeastern Alaska and draws milder air northward. This storm also is expected to bring the potential for heavy snow across the south-central/southeastern mainland (especially the Copper River Basin area) late Sunday into Tuesday before shifting southward across the entire Panhandle Tuesday into Wednesday (where both rain and snow are expected). Arctic air building in behind this system will again push temperatures well below normal, with the core of the coldest air expected over western Alaska and the eastern Aleutians. Klein