US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 322 PM EDT Fri Oct 25 2019 Valid Monday October 28 2019 - Friday November 01 2019 Hazards: - Heavy rain across portions of the Lower Mississippi Valley, the Tennessee Valley, the Middle Mississippi Valley, the Mid-Atlantic, the Southern Appalachians, the Southeast, and the Southern Plains, Tue-Wed, Oct 29-Oct 30. - Heavy rain across portions of the Northeast, the Central Appalachians, the Mid-Atlantic, the Southern Appalachians, the Great Lakes, and the Ohio Valley, Thu-Fri, Oct 31-Nov 1. - Heavy snow across portions of the Central Rockies, the Central Plains, and the Southern Plains, Tue, Oct 29. - Heavy snow across portions of the Middle Mississippi Valley, the Great Lakes, and the Upper Mississippi Valley, Mon, Oct 28. - Flooding possible across portions of the Northern Plains. - Flooding occurring or imminent across portions of the Middle Mississippi Valley, the Upper Mississippi Valley, and the Northern Plains. - Flooding likely across portions of the Northern Plains. - Much below normal temperatures across portions of the Central Plains, the Central Rockies, the Central Great Basin, the Northern Plains, the Northern Rockies, the Southern Rockies, the Middle Mississippi Valley, the Northern Great Basin, the Upper Mississippi Valley, the Southern Plains, and the Southwest, Mon-Wed, Oct 28-Oct 30. - Much below normal temperatures across portions of the Central Plains, the Central Rockies, the Lower Mississippi Valley, the Central Great Basin, the Northern Plains, the Tennessee Valley, the Great Lakes, the Northern Rockies, the Southern Rockies, the Middle Mississippi Valley, the Northern Great Basin, the Upper Mississippi Valley, the Southeast, the Southern Plains, the Ohio Valley, and the Southwest, Thu-Fri, Oct 31-Nov 1. - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Mon-Thu, Oct 28-Oct 31. - Heavy precipitation across portions of the Alaska Panhandle, Fri, Nov 1. - Much above normal temperatures across portions of mainland Alaska, Mon-Thu, Oct 28-Oct 31. Detailed Summary: Much of the contiguous U.S. will experience some significant weather-related hazard next week, especially with respect to temperatures. At the start of the period, Monday, a cool Canadian air mass will be in place from the Rockies/Great Basin eastward across the northern and central Plains. A reinforcing shot of arctic air will push into the northern Rockies by later Monday and drop into the central Rockies by Wednesday morning, maintaining much below normal temperatures across this same region through at least Wednesday. Temperatures will average upwards of 20-30 degrees below normal, with below zero readings likely across parts of the Northern Rockies. In addition to the cold air, a surface low pressure area moving along the front separating the arctic air from milder conditions to the east may produce a stripe of locally moderate to heavy snows across the upper Mississippi Valley on Monday. The confidence with this system is very low, as there have been large differences among the guidance handling this pattern. Right now, we've got the band of snow stretching from northeastern Iowa into central Wisconsin, but it's probably going to shift somewhat as the model solutions begin to converge this weekend. While total accumulations won't likely be too heavy, it would be the first snow of the winter season for this region. On Tuesday, a strong short wave trough will drop into the central Rockies, and combined with moist upslope flow, will support the threat of moderate to heavy snowfall from southeastern Wyoming through eastern and central Colorado through Tuesday evening. From late Wednesday through Friday, the cold air mass will make its way eastward and southward, with much below normal temperatures spreading into the southern plains and central and lower Mississippi valleys. Expect temperatures around 15-20 degrees below average, with many of these areas experiencing their first freeze of the fall Thursday and Friday mornings. Ahead of the strong cold front, a flow of deep Gulf of Mexico and Atlantic moisture will feed into the southern and southeastern states and bring the threat for a widespread area of moderate to heavy rainfall. For Tuesday into Wednesday morning, the focus for the heaviest precipitation will be over the lower Mississippi valley and eastern Oklahoma/Texas as the deep moisture overruns the frontal boundary. During Wednesday, a series of weak short waves lifting along the western periphery of upper level high pressure in the southwestern Atlantic will combine with convergence along the remnants of a weak boundary to potentially spread showers and thundershowers eastward through the section of the southeastern states, southern mid-Atlantic states and Tennessee Valley. Upslope flow could help enhance precipitation amounts over the southern Appalachians. As low pressure advances northeastward along the strong cold front, moderate to heavy rainfall will spread into the rest of the mid-Atlantic states and Northeast Thursday-Friday. There is a lot of uncertainty with this forecast as the model solutions vary considerably during the mid-latter part of next week. As a result, confidence in this hazard area is quite low. Across Alaska, the pattern at the start of the period will be highly amplified, with a deep closed low over the Bering Sea and a strong ridge downstream extending from the Alaskan panhandle northward along the Alaska/Yukon border. Strong southerly flow in advance of the low will tap deep moisture from the subtropics and bring heavy precipitation (rain at low elevations, snow in the mountains) into the southeastern part of the mainland along a north-south aligned cold front. Precipitation amounts will range upwards of 2-3 inches, with locally higher amounts in favored upslope regions. This plume of moisture will push eastward and lose its connection to the tropics on Tuesday, but there is still persistent onshore flow across the south-central and southeastern mainland associated with short wave energy rotating around the closed upper low. This will maintain the threat for widespread precipitation, though amounts will be lower than Monday. Another low pressure area is likely to impact the mainland during the mid-latter part of next week. There are again model discrepancies, but the general consensus is that strong onshore flow will resume later Wednesday into Thursday ahead of this system across the southern coast of the mainland. This should bring another round of heavy precipitation across much of the same areas impacted during the early part of the week. Finally by Friday, the axis of precipitation is expected to shift southward, with heavy rain/mountain snow impacting much of the panhandle region. In addition to the heavy precipitation, the strong southerly flow ahead of the deep Bering Sea low will allow warmer than normal air to overspread the state. Temperatures across the North Slope and sections of Brooks range will average 20-25 degrees above normal through the mid part of next week. An influx of arctic air will allow temperatures to return to more normal levels by late week. Klein