US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 248 PM EST Mon Nov 22 2021 Valid Thursday November 25 2021 - Monday November 29 2021 Hazards: - Heavy rain across portions of the Southern Plains, Thu, Nov 25. - Heavy precipitation across portions of the Pacific Northwest and the Northern Great Basin, Thu, Nov 25. - Heavy rain across portions of the Pacific Northwest and the Northern Great Basin, Thu-Fri, Nov 25-Nov 26. - Much below normal temperatures across portions of the Southeast and the Mid-Atlantic, Thu, Nov 25. - Much below normal temperatures across portions of the Middle Mississippi Valley, the Lower Mississippi Valley, the Ohio Valley, and the Tennessee Valley, Fri, Nov 26. - Much below normal temperatures across portions of the Southeast and the Southern Appalachians, Sat, Nov 27. - Heavy precipitation across portions of the Alaska Panhandle, Thu, Nov 25. - Much below normal temperatures across portions of mainland Alaska, Thu-Mon, Nov 25-Nov 29. Detailed Summary: During the medium range period (Thursday, November 25th - Monday, November 29th) instances of active weather are in store for the eastern two-thirds of the country as a deepening upper-level trough progresses from the Great Plains to the Northeast. Beginning on Thanksgiving Day, wet weather will be felt from the the Upper Great Lakes to southern Texas as showers and thunderstorms develop along and ahead of a cold front extending between the two regions. Rainfall accumulations are expected to be light given the generally progressive nature of the front, however, a slower paced southern edge interacting with an influx of Gulf moisture will allow for rainfall totals in southeast Texas to reach 1 to 2 inches in 24 hours. Though these conditions may raise concerns for flash and urban flooding, the recent lack of heavy precipitation in the region and unsaturated soils will likely limit any flooding to isolated instances. By Friday the cold front is forecast to reach the Eastern Seaboard while an associated low pressure wave moves into southern Ontario. As the front passes through the Northeast cold air pulled southward on the back side of a newly developed low pressure center will allow for mixed precipitation types ranging from rain to light snow to fall from the Central Appalachians through interior New England. The greatest snowfall accumulations are anticipated downwind of the Lower Great Lakes as well as in the higher elevation Adirondack, Green and White Mountains. Further west, a series of Pacific systems are forecast to approach the Pacific Northwest, continuing the wet and snowy pattern over the region. The first system will approach the coastline Thursday, funneling a significant amount of moisture from the tropics onshore. Though most of this moisture is expected to fall as heavy rain through Friday evening, in the higher terrain of the northern Washington Cascades snow levels will be low enough on Thursday to allow for some moderate accumulating snowfall. As moisture associated with this system moves further inland later in the day, rain and high elevation snow will to spread into the Northern Rockies and continue through Friday. Meanwhile, a tight pressure gradient set up along the lee side of the North/Central Rockies will generate some gusty, non-hazardous winds from Thursday morning to Friday afternoon. Without skipping a beat the second Pacific system is forecast to reach western Washington on Saturday morning bringing another, though less intense, round of rain and high elevation snow to the northern portion of the state. Temperature-wise a see-saw pattern is forecast to set up over the CONUS, with warmer than normal temperatures blanketing the West and Great Plains while near or colder than normal temperatures persist elsewhere. Though no sizable temperature anomalies below average are expected throughout the period, some areas will be cooled to the extent that they experience a first freeze, a first hard freeze, or temperatures low enough to possibly damage vegetation. The first area to be affected during the medium range will be the Southeast on Thursday with an impacted area extending from Georgia to North Carolina. Though overnight lows in these states will only be sitting around 8 to 9 degrees below normal, many areas within the highlighted region will likely experience their first freeze below 32 degrees including some susceptible vegetation in Georgia. The following day temperatures from the Lower Mississippi Valley to the Ohio Valley are expected to fall following the passage of the previously mentioned cold front. The greatest drop in overnight lows is forecast from northern Arkansas to central Illinois where temperatures will drop 10 degrees or more into the mid to low 20s, giving some areas their first hard freeze of the year. As the cold airmass moves east temperatures in the Southeast will once again take a hit on Saturday falling 10 degrees to at or below freezing once more, this time affecting susceptible vegetation in both Georgia and Alabama. Switching focus to Alaska, at the beginning of the period a deep low pressure/frontal system remaining virtually motionless over the Gulf will draw a significant amount of lower latitude moisture northward before redirecting it into the southern half of the Alaska Panhandle. With liquid precipitation in excess of 2 inches forecast to move onshore, heavy coastal rain and inland mountain snow is expected to fall over the region Thursday into Friday. A second round of heavy precipitation will be possible early next week over the same area, however, there is a large amount of uncertainty among the current guidance with respect to if heavy precipitation will occur and if it does how much will fall where. As such, no heavy precipitation area has been drawn at this time. With regard to temperature, frigid below average highs and lows are forecast for much of the mainland throughout the period. The southwestern and western portions of the mainland are expected to experience the most persistent and severe temperature anomalies, where temperatures are on track to plummet 20+ degrees below normal throughout the period. With nighttime temperatures falling to and below -30F in some areas, residents should limit time outdoors and take the proper precautions to prevent the onset of frostbite and/or hypothermia. Zavadoff