US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 328 PM EST Thu Nov 18 2021 Valid Sunday November 21 2021 - Thursday November 25 2021 Hazards: - Heavy precipitation across portions of the Northeast, Mon-Tue, Nov 22-Nov 23. - Heavy rain across portions of the Lower Mississippi Valley and the Southern Plains, Thu, Nov 25. - Heavy rain across portions of the Northeast, Mon, Nov 22. - Flooding occurring or imminent across portions of the Pacific Northwest. - Much below normal temperatures across portions of the Upper Mississippi Valley and the Northern Plains, Mon, Nov 22. - Much below normal temperatures across portions of the Southeast, the Southern Appalachians, and the Tennessee Valley, Mon-Tue, Nov 22-Nov 23. - Heavy precipitation across portions of the Alaska Panhandle, Sun, Nov 21. - High winds across portions of the Alaska Panhandle and mainland Alaska, Sun-Mon, Nov 21-Nov 22and Wed-Thu, Nov 24-Nov 25. - Much below normal temperatures across portions of mainland Alaska, Sun-Tue, Nov 21-Nov 23. Detailed Summary: The medium range period (Sunday, November 21st -- Thursday, November 25th) will feature hazardous weather in the Northeast and Lower Mississippi Valley thanks to the presence of two potent mid latitude cyclones. In the case of the first system, an amplified pattern at 500mb, with ridging over the Rockies and troughing in the east will lead to the latter generating a potent mid-latitude cyclone that will go on to produce heavy precipitation and winds for parts of the Northeast on Monday. Models seem to be coalescing around a faster and warmer solution compared to their previous runs. This means that heavy rain/snow is likely across interior portions of the Northeast, i.e. northern New England, while a strictly heavy rain event will unfold over eastern Maine. Deterministic models are suggesting anywhere from 1-3 inches of rain with locally higher amounts possible while ensemble means promoting a less robust output, with totals tamped down to around 1 inch on Monday. Winds are expected to pick up on the backside of this system between Monday and Wednesday. The cold front associated with this system will sweep through the east coast and usher in a period of cooler weather beginning Monday night as high pressure begins to build across the region. Sensitive soils and first freeze potential in northern Alabama/Georgia and the Southeast coast respectively led to the issuance of much below temperatures on Tuesday night into Wednesday. Low temperatures are likely to bottom out in the upper 20s to low 30s in these areas. High pressure in the Plains will plummet temperatures into the single digits over northeastern North Dakota and northwestern Minnesota on Tuesday. Wind chills could exacerbate the cold associated with this air mass which is why a much below normal temperatures hazard was issued for the area. A noticeable increase in model confidence, particularly with respect to the EC and GFS means, has led to the introduction of a heavy rain hazard for much of the ArkLaTex region as well as portions of western Mississippi and southeastern Oklahoma on Thanksgiving day. An amplified trough will emerge from the Southern Rockies on Thursday and jump start a frontal system over the Plains by pulling substantial moisture from the Gulf of Mexico into the Southern Plains and Mississippi Valley that day. Elsewhere across the CONUS, seasonal temperatures in the west and showers for the Pacific Northwest are expected next week. For Alaska, an active pattern along the Gulf coast will produce substantial precipitation over the southeast coast and high winds along much of the coast next week. The first in a series of low pressure systems will arrive in the central Gulf coast on Sunday, generating high winds and mixed precipitation across the central and southeastern coasts through Monday. Anomalously high precipitation is likely for small portions of the southeast panhandle and into British Columbia on Sunday and Monday due to moisture advection associated with this system. There will be a brief lull in activity on Tuesday before another system arrives on Wednesday and picks up on the high wind threat across the coast through Thanksgiving. Kebede