If you are spending Valentine's Day in the Ohio Valley, Mid-Atlantic, Northeast or even parts of the South this year, you may want to plan on a romantic evening indoors.
A potentially historic cold snap coming straight out of the Arctic is projected to send temperatures tumbling to about 30 degrees below average on Saturday and Sunday, creating a formidable obstacle to getting to that mediocre prix fixe meal that you so carefully planned for you and your date.
In New York City, the low temperature on Sunday morning may be in the single digits or possibly even below zero degrees Fahrenheit, with even colder conditions for Sunday night. (The actual low will depend on whether the city has much snow cover, since snow is efficient at radiating heat back out into space.)
Similar unusual cold is anticipated for cities like Columbus, Ohio, Washington, D.C., and Pittsburgh, as a lobe of the tropospheric polar vortex briefly settles in for a stay smack dab on top of the region.
Even the Southeast will be colder than average, with temperatures struggling to make it much above 32 degrees Fahrenheit, or 0 degrees Celsius, in parts of the Carolinas, Tennessee and Georgia during the weekend.
The cold snap has ties to events high above the North Pole, where a sudden stratospheric warming event that has been unfolding for more than a week now is working to periodically dislodge portions of the tropospheric polar vortex and fling them southward.
The precise mechanics of how stratospheric warming events can disturb the polar vortex in the troposphere is not fully known, but it is generally understood that such warming events can be followed within one to two weeks by colder than average temperatures in North America, Europe or Asia.
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Sudden stratospheric warming events occur when large atmospheric waves, known as Rossby waves, disturb the ultra cold, thin air in the stratosphere.
This jolt of energy delivered to the upper atmosphere can set in motion a process that can in turn destabilize the high altitude low pressure area that spins around the North Pole during the winter.
This low pressure area is more commonly known as the polar vortex.
When the circulation around this low is strong, little frigid air spills south out of the Arctic. But when the winds slow, the low tends to wobble, like a spinning top becoming less stable as it slows down. This can caused sudden surges of frigid air to slide southward, out of the Arctic.
During some stratospheric warming events, the polar vortex can split in two, bringing ultra-cold air for long periods of time to parts of the world.
That does not appear to be happening now.
Judah Cohen, director of seasonal forecasting at AER, a private forecast company in Massachusetts, told Mashable that the warming event in the polar stratosphere may be in the top two such events on record, judging by the temperature spike.
"The warming event at the Pole is looking to be top two," he said, adding that the projected temperatures in the stratosphere will be close to the boiling point of water at that altitude.
He said forecasters are not unanimous in thinking how the cold weather will play out during February.
"I think it is a significant event that will have repercussions on the troposphere's weather for weeks to come; others feel this is no big deal and will not have a lasting impact on tropospheric weather beyond a day or two," he said, regarding conversations with other forecasters.
Typically, sudden stratospheric warming events exert the most influence on weather patterns about two weeks later. However, that may not always be the case, Cohen said in an email to Mashable.
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"I strongly believe that the sudden stratospheric warming event and the Valentine cold are strongly related," Cohen said. "Even though weather impacts associated with the polar vortex events are only supposed to occur with a 10 to 14 [day] delay, I have noticed over the past couple of winters there does seem to be an almost immediate response followed by the delayed response."
The peak in this stratospheric warming event is likely to occur on Wednesday, he said, with the cold outbreak in the U.S. to follow a few days later. Then, around Feb. 20, another cold outbreak is likely, he said, this time related to the delayed response.
For now, though, if you don't have a date for Valentine's Day, you should make more of an effort to get one, simply to stay warm.
