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CHARLOTTE, N.C. (PINPOINT WEATHER) — So far, this winter has been more of the same for the Carolinas.
Generally, that’s meant mild temperatures with a brief and fleeting cold snap or two like what we saw in the middle of January. It has been 739 days since Charlotte last saw a flake of snow, the longest drought in recorded city history.
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Potentially though, the overall large-scale weather pattern will begin to shift colder for a potentially wintry setup for the eastern half of the country in the second half of the month and into March.
There are two large-scale patterns, or what’s called teleconnections, that meteorologists watch for when trying to determine the timing of cold and snow being more likely to occur across the eastern third of the country. The first is what is called the Arctic Oscillation or “AO.” The AO is a way to measure the strength of the Polar Jet Stream and Vortex near the North Pole.
When it is in its positive phase, Arctic air tends to be locked up closer to the pole with very cold temperatures compared to average in northern Canada and Alaska, but mild air dominates the Continental U.S. When it is in its negative phase, the opposite is true, meaning a weaker polar vortex and Jet Stream, allowing cold air to spill south across the lower 48 states.
Another very important pattern we look at is the North Atlantic Oscillation or “NAO.” The NAO is a measure in the difference in pressure between the Subtropical High and Subpolar Low in the Atlantic Ocean. When the NAO is in its positive, there is a trough of low pressure over the North Atlantic, usually meaning a ridge over the Southeast, forcing storms system to cut up to our west into the Ohio Valley. When in the negative phase, large blocking high is placed near Greenland with colder weather across the eastern third of the country along with more coastal storms.
Looking toward the second half of February, it is increasingly likely that both will be in their negative phase meaning below-average temperatures are likely for the eastern half of the country. While colder temperatures are likely, that does not mean snow is a lock for the Carolinas later this month.
It takes a near perfect setup for snow, and while the pattern says it’s possible, that’s different than saying it will happen. In the meantime, stay with your Pinpoint Weather Team for the latest updates this winter!