US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 314 PM EST Mon Nov 23 2020 Valid Thursday November 26 2020 - Monday November 30 2020 Hazards: - Heavy rain across portions of the Lower Mississippi Valley, the Tennessee Valley, the Mid-Atlantic, the Southern Appalachians, the Southeast, and the Southern Plains, Thu-Sun, Nov 26-Nov 29. - Flooding occurring or imminent across portions of the Southeast and the Mid-Atlantic. - Heavy precipitation across portions of mainland Alaska and the Aleutians, Thu-Fri, Nov 26-Nov 27 and Sun, Nov 29. - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Sat-Mon, Nov 28-Nov 30. - High winds across portions of the Alaska Panhandle and mainland Alaska, Fri-Mon, Nov 27-Nov 30. - High winds across portions of mainland Alaska and the Aleutians, Thu-Mon, Nov 26-Nov 30. Detailed Summary: The final days of November feature a quick moving disturbance over the northern Mid-Atlantic on Thanksgiving that favors a wet day in parts of the Northeast. From a big picture standpoint, the Thanksgiving disturbance in the Northeast is just the appetizer to the main course this weekend; a disturbance breaking off of a long-wave trough tracking across the Upper Midwest. This disturbance likely becomes a cut-off upper low over the Southwest where it is likely to produce some higher elevation snowfall in the southern and central Rockies this Friday and into Saturday. This upper low and a low level frontal boundary over the Deep South are the keys in determining which areas of the South receive heavy rainfall. Upper lows are notoriously pesky and are known to be modeled to eject east out of the Southwest too quickly. In addition, ensemble guidance show differing strengths of the upper low with the EPS the strongest among itself, the GEFS and Canadian ensembles. That said, upper level divergence ahead of the trough and better frontogentical forcing is likely to occur from eastern Texas to the Lower Mississippi Valley where all three ensemble models pin point the heaviest amounts Friday into Saturday. By Sunday, the Deep South should be favored to remain wet but exactly where the heaviest amounts take place will be determined by the strength and forward speed of the upper trough. Precipitation may then spread up the East Coast by the start of next week once a new upper level disturbance dives south from central Canada and acts to speed up the progression of the southern storm system. The Lower 48 remains void of temperature hazards to conclude November. The 5-day mean temperature anomalies in the East range from 4-8 degrees above normal. The coolest locations versus normal are forecast to occur from the Intermountain West and southern Plains to the Lower Mississippi Valley. For the southern regions in particular, the slightly cooler temperatures are a result of clouds and rainfall limiting daytime highs and keeping overnight lows seasonally mild. The area with the most potential hazards to close out the month of November is Alaska. Along with above normal temperatures throughout much of "The Last Frontier", the southern tier of the state is set to be battered by a pair of powerful storm systems starting first with an intensifying low pressure system near the Aleutians on Thanksgiving. The storm deepens further over the Bering Sea on Friday with strong winds and heavy showers over the Aleutians and up the southwest peninsula. Friday into Saturday is set to be the most unsettled period for the southern mainland coast and towards the Panhandle. Copious amounts of mountain snow and coastal/valley rain are expected with snow in the higher elevations being measured in feet. High winds will also make for high surf along the coasts. In addition, treacherous travel conditions are likely where snow levels are low as the combination of heavy snow and gusty winds cause whiteout conditions at times. While conditions may improve briefly along the southern coast and the Panhandle on Sunday, it will be very short lived as yet another strong cyclone reaches the Aleutians. Some ensemble guidance suggests this storm may have as much, if not more, atmospheric moisture to work with due to the storm's moisture source stemming from the subtropical West Pacific. Look for conditions to deteriorate again in the Aleutians and southwest Peninsula late Saturday into early Sunday, followed by the southern coast and Panhandle late Sunday into Monday. Expect similar impacts to the first storm, although wind speeds and areas of high surf are slightly lower in confidence. While there is still some disagreement on timing and track, ensemble guidance supports a stormy signal to close out the month of November. Mullinax