Rumors have been flying. A Facebook page, "Weather Boy Weather," posted a map predicting up to 30 inches would fall from Wednesday night into Thursday.
The National Weather Service posted a more-conservative snow-accumulation map, calling for six to eight inches in the immediate Philadelphia area by 7 a.m. Thursday.
Why the rush, particularly for a dicey forecast likely to be a work in progress until the storm pulls away?
Yes, computers were making a case for those amounts, but another big factor, said Gary Szatkowski, meteorologist in charge of the National Weather Service, was social media.
Szatkowski said the office wanted to get a reasonable and scientifically based estimate out there before someone proclaimed that 40 inches of snow was about to descend upon Philadelphia, with a 20 percent chance of the end of Western civilization in the northern and western suburbs.
The real potential is foreboding enough, as the weather service issued a winter-storm watch for the entire region for six to 10 inches of snow and perhaps more ice.
And the Weather Boy map, posted late in the day, was legitimate. But it was generated from a computer model whose performance, two days away from a storm, is considered suspect in the meteorological community.
Dave Tolleris, meteorologist with the private service Wxrisk.com, noted that it was a Facebook site that beat the drum for a 30-inch snowstorm for Saturday and Sunday.
So the forecast was off by 27.3 inches.
Philadelphia did get 2.7 inches, bringing the seasonal total to 43.3, nudging the winter of 1957-58 out of 10th place.
On any given day, a computer model is likely to see a megastorm on the horizon. Meteorologists, who are using social media more themselves, complain that with so many models available for plucking and misinterpreting, Twitter and Facebook can propagate storms of bad information.
Those, in turn, can induce panic among citizens. Not that your local supermarkets are complaining.
"Social media is a negative factor," said Dan Kottlowski, a meteorologist with AccuWeather Inc., the commercial service in State College, Pa. "Any Tom, Dick, and Harry can look at the computer models. It's human nature to see the worst-case scenario."
Computer models for this particular storm have been offering a variety of unappealing scenarios, but all agreed Monday that the storm would begin with significant snowfall Wednesday night.
What happens early Thursday remained unresolved. Unlike other storms this season, this one will be an old-fashioned nor'easter - so named for the winds from the northeast that they generate - juiced with Gulf moisture.
Heavy snow could be followed by a period of ice and/or rain, particularly from the I-95 corridor south and east. Expect details to change between the time you read this and when something starts falling - even after it starts falling.
Szatkowski himself did take to Twitter on Monday morning, opting for humor over hype.
"Now, I'm hearing moaning & groaning about more snow," he tweeted. "Put things in perspective. At least we haven't issued a 'glacier watch' (yet)."