Before this weekend’s storm had dropped so much as an inch of snow, meteorologists were already rushing to dismantle rumors that another potentially more potent one was lurking in the following week’s forecast.
The chatter began on Friday, when one of the many prediction models forecasters use showed a classic nor’easter: a storm that would take shape in the Gulf of Mexico, sweep across southern Georgia and hug the Atlantic Coast as it trekked north. The hypothetical simulation bore a striking resemblance to the “Storm of the Century” in 1993, which brought widespread heavy snow and paralyzed the East Coast for days.
But hold on a moment.
First, an explanation of how meteorologists build a forecast. There are two main computer models used around the world — the American (GFS) model and the European (ECMWF) model — that can visualize the overall weather pattern up to 14 days in advance. That far ahead, most of the information they spit out is hypothetical, though not always.
The storm showed up on several runs of the American model on Friday. By Saturday and Sunday, that same model failed to replicate the scenario. Other models, including the European one, began to hint at a similar system, but they placed it too far offshore to produce meaningful precipitation.
Dylan Lusk, a meteorologist with the Atlanta office of the National Weather Service, addressed the speculation on Saturday in his morning forecast. After giving a brief summary of the ice expected in his region this weekend, he turned to what he called his “favorite PSA.” “Friends don’t let friends share single model runs of 10:1 snow totals 8 to 9 days out on social media,” he scolded. “From any model. Yes, I am judging you for posting that GFS run.”
Luke Culver, also with the Atlanta Weather Service office, expressed similar skepticism that afternoon: “Storm Threat Late Next Week? (Spoiler: Very Unlikely),” he wrote.
Mr. Culver, too, sought to tamp down online speculation:
“You may have heard about or seen posts on social media regarding a snow or winter weather threat in Georgia late next week or next weekend,” he wrote. “Well, at this time, that threat appears to be very low.”
But with Arctic air bringing usually cold temperatures across the South this week, forecasters acknowledge that the atmosphere is primed for more winter weather.
They are currently navigating what Eric Fisher, the chief meteorologist for WBZ-TV in Boston and an author of a book on major storms, called a “funnel” of uncertainty. Seven days out, meteorologists rely on pattern recognition to suggest what a storm is likely to do. As a storm draws closer — within 24 to 48 hours of arrival — and its specific physics become clearer, meteorologists can focus on the most likely scenarios.
On Sunday morning, the Weather Prediction Center, an arm of the Weather Service, noted that the current pattern in the atmosphere sets the stage for more winter precipitation in parts of Texas later this week.
For now, the only circumstance forecasters are confident about is the bitter cold that is settling in across the United States that will remain in place for days.
Freezing temperatures are the primary ingredient for winter weather, and they will be present across the Southeast. While Sunday’s model runs show weak signals for snow in cities from Atlanta to New York during the first two days of February, these models are outliers in what is otherwise a dry, cold outlook.
The takeaway: Be wary of the snowflake icons on your weather app seven days out, and be skeptical of social media posts that promise feet of snow a week in advance.
If these outliers become a consistent trend — that is, if more of the model runs begin to converge on the likelihood of this next storm — forecasters will begin to take the threat more seriously, especially given how sensitive local infrastructure remains after this weekend’s ice and snow.
For now, Mr. Culver had one piece of advice: “Let’s get through this weekend’s ice storm first.”
Judson Jones is a meteorologist and reporter for The Times who forecasts and covers extreme weather.
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