US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 407 PM EDT Mon Oct 19 2020 Valid Thursday October 22 2020 - Monday October 26 2020 Hazards: - Heavy rain across portions of the Central Plains, the Lower Mississippi Valley, the Tennessee Valley, the Great Lakes, the Middle Mississippi Valley, the Southern Plains, and the Ohio Valley, Sun-Mon, Oct 25-Oct 26. - Heavy rain across portions of the Southeast, the Great Lakes, and the Upper Mississippi Valley, Thu-Fri, Oct 22-Oct 23. - Heavy rain across portions of the Northeast and the Great Lakes, Mon, Oct 26. - Heavy snow across portions of the Northern Plains, the Northern Rockies, and the Northern Great Basin, Fri-Sat, Oct 23-Oct 24. - Heavy snow across portions of the Central Rockies, the Central Plains, the Central Great Basin, the Northern Plains, and the Northern Rockies, Sat-Sun, Oct 24-Oct 25. - Heavy snow across portions of the Upper Mississippi Valley and the Northern Plains, Thu, Oct 22. - Flooding occurring or imminent across portions of the Lower Mississippi Valley. - Much below normal temperatures across portions of the Central Plains, the Central Great Basin, the Northern Rockies, the Central Rockies, the Northern Great Basin, and the Pacific Northwest, Sun-Mon, Oct 25-Oct 26. - Much below normal temperatures across portions of the Northern Plains, the Northern Rockies, and the Northern Great Basin, Thu-Mon, Oct 22-Oct 26. - Much below normal temperatures across portions of the Central Plains, the Northern Plains, the Northern Rockies, the Central Rockies, the Middle Mississippi Valley, and the Upper Mississippi Valley, Fri-Mon, Oct 23-Oct 26. - Heavy precipitation across portions of mainland Alaska and the Aleutians, Thu-Fri, Oct 22-Oct 23. - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Sun-Mon, Oct 25-Oct 26. - Heavy snow across portions of mainland Alaska, Thu-Fri, Oct 22-Oct 23. - High winds across portions of mainland Alaska and the Aleutians, Thu-Fri, Oct 22-Oct 23. Detailed Summary: An increasingly wintry weather pattern throughout the northern Rockies and Plains becomes the story of the medium range (Thurs. Oct 22 - Mon. Oct 26). The upper level pattern features an expansive upper level ridge over the northeast Pacific, a deep upper trough in central Canada and the north-central U.S., and upper level ridging over the northwest Atlantic. The resulting weather pattern forces a series of frigid Canadian air-masses to plunge south into the Nation's Heartland. The northern High Plains and Rockies will be subjected to a prolonged stretch of very cold temperatures. Temperatures throughout a large portion of Montana will see daily minimum temperatures fall into the single digits. High temperature anomalies look to range between 25 to 35 degrees below normal throughout Montana and into the Dakotas. Other parts of the central High Plains and Upper Midwest can also anticipate a more winter-like temperature regime Friday and into Saturday. A second and more potent shot of colder temperatures should advance through the Northwest, northern Great Basin and into the central Plains and Upper Midwest this Sunday and into early next week. Heavy snow is also in the fold across the Upper Midwest on Thursday and in the northern Rockies and High Plains this Friday and Saturday. Snow totals may reach double digit totals in the higher elevations of the northern Rockies by this weekend. Farther east, as upper-level troughs dig south into the North-Central U.S. this weekend, and eventually into the central Plains by early next week, unseasonably warm temperatures look to develop across the eastern third of the U.S. late week. Temperatures look to return to more seasonably levels in the Northeast by this weekend, but abnormally warm conditions look to persist in the Southeast. As a surface low responsible for the heavy snow in the Upper Midwest tracks into the northern Great Lakes on Friday, heavy rain is also anticipated in portions of these regions. Farther south, a surface trough and nearby tropical moisture may lead to heavy rainfall along portions of the central Gulf Coast. Lastly, another upper level trough swinging through the Rockies and central Plains look to bring about a new chance for heavy rainfall from the Mississippi and Ohio Valleys to the Great Lakes and interior Northeast this coming Sunday and Monday. Over Alaska, an impressive and stout upper level low is forecast to pass over the Aleutians and occlude in the Bering Sea by the start of the weekend. This storm system is tapping into subtropical moisture and may generate anywhere from 2-3" worth of liquid precipitation from the Upper Peninsula to Kodiak Island. Higher elevations should receive heavy snow while the primary precip type stays rain along the coast and lower elevations. Heavy snow in the mountain ranges of southwest Alaska are also likely along with strong gales that include wind gusts in excess of 60 mph along the coast. As that storm gradually weakens by the end of the weekend, a new storm system is expected to form in the Gulf of Alaska that then sends heavy precipitation into the northern Gulf Coast on south and east into the Panhandle. There is still some spread in model guidance so exact details in terms of totals and timing are still subject to change, but the setup should yield heavy coastal/valley rain and heavy mountain snow to close out the weekend and open next week. Mullinax