All 50 states have seen snow two weeks ahead of Christmas
Wednesday, December 13, 2017, 10:26 - As of December 12 2017, 23.6% of the U.S. surface is covered with snow, but what is especially striking is that more than two weeks before Christmas day, all 50 states have seen snow on the ground despite much of it rapidly melting away in some areas. December marks a turning point towards more wintry weather, but it is not so common to see so much snow on the ground this early, especially in some areas of the south and more so with La Niña influencing U.S. weather.
Potent snow storm blankets the South
A total of 17 states saw snowfall (see video below) in one degree or another late last week as a very active cold front colored in white a large swath extending diagonally from New Mexico and Texas, to New England. Record breaking snow of a foot or more was recorded in some counties of Alabama, Georgia and North Carolina.
This storm was certainly the main contributor in terms of snow reaching states that normally do not see it until later in the season. Starting in southwest Texas and southeast New Mexico last Thursday, it then moved across much of the Southeast on Friday and eventually into the northeast U.S. by Saturday.
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The snow even extended into the mountains and high desert areas of northern Mexico, but it was unbelievable was too see more than a foot of snow across some areas of the Deep South once the storm was over. Sea surface temperatures in the Gulf of Mexico and off the Eastern Seaboard are 2 to 4oF higher than usual, and in some cases even higher. As this active weather system tracked east, it tapped in a considerable amount of moisture from the ocean, producing incredible amounts of snow especially along the southern end of the Appalachians.
Snow cover as of Dec. 13
Northeast Alabama, northern Georgia and extreme west North Carolina, saw the greatest amount of snow, with remarkable depths in Mount Mitchel, N.C.: 25.0 inches; Delta, La.:15.0 inches; and Clayton, Ga.: 14.0 inches. The list of larger urban areas with snow is also impressive, with Atlanta at the top as some sections of the metro area received close to 8.0 inches. Corpus Christi, Texas, and Jackson, Mississippi, saw more than 5 inches.
Not a weather pattern expected with La Niña
After the very mild winter experienced in many areas of the south and east this year, seeing snow in all 50 states, and especially in the deep south this early in the season has certainly come as a surprise. Even more so, knowing we are in a La Niña mode, which normally means warmer and drier weather for many portions of the south and east.
Map showing animated SST anomalies Pacific from NOAA<</em>
The effects of La Niña on U.S. weather are already noticeable, but positive SST anomalies in many other ocean areas surrounding North America also need to be considered as they can impact certain weather events like the recent snow storm in the south.
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There is a wide consensus among model forecasts that La Niña could even strengthen in the equatorial Pacific during the coming weeks and a 65 to 75% chance it will continue during the winter months. Despite being a weak La Niña, we should still expect this tropical pattern to influence US weather this winter.
Looking ahead to Christmas
Arctic air relaxes this weekend and into early next week but arctic air is expected to take over many areas east of the Rockies leading up to and through Christmas with the potential for an active pattern impacting travel heading into the holidays as southeastern ridge fights back. An abundance of arctic air expected for the Plains and spreading east during the holidays.