Archive: January, 2011
The last of the heavier bands of snow is moving through the western suburbs, and then the snow should back off -- for awhile.
So far, reports of 4 and 5 inches are common, says Bob Wanton at the National Weather Service office in Mount Holly.
He expects light mixed precipitation this afternoon, and then the main event arrives.
Obviously prompted by this morning's surprisingly vigorous snowfall, the National Weather Service is adusting its accumulation forecasts upward.
It's now saying that up to a foot could fall before it's all over before daybreak tomorrow.
That would make sense, given that so far up to 4 inches has been reported in the Pennsylvania suburban counties.
The National Weather Service hasn't posted totals yet, but 3 and 4 inches are being reported north and west of the city with moderate to heavy snow still falling in some areas.
Radar shows the snow-mix line continues to press north and west toward Philadelphia, and temperatures everywhere are very close to freezing.
The accumulating snow is supposed to shut off in the next hour or so and give way to lighter, mixed precipitation for most of the rest of the day.
So far, 1 to 2 inches of snow has been measured in parts of the region, and, yes, this was not supposed to happen.
The snow should back off in the next hour or two, said Bob Wanton, meteorologist at the National Weather Service office in Mount Holly, but it may be too late to save the morning rush.
Mixed precipitation on the light side is expected the rest of the day, and the main event -- heavy snow with an additional 4 to 8 inches -- isn't due to show up until around 5 or 6. Thundersnow remains a possibility.
Scattered snow placed a powdered-sugar coating on parts of the region this morning, and a period of heavier snow scooted to the northeast of the region.
It wasn't much, but it could be a big player tomorrow night, according to Louis J. Uccellini. He runs the National Centers for Environmental Protection and one of the nation's foremost winter-storm experts.
It already has had an impact on the forecasts.
Computer models have been all over the place on snow totals for the coming storm, but this morning the U.S. North American Model went on tilt.
The most-recent run showed a major snowstorm for the immediate Philadelphia area, and the National Weather Service is considering bumping up the advisories.
Right now, it has a winter-storm watch for Montgomery and Bucks Counties, but it says it is weighing extending it all the way into South Jersey.
The region is about to experience its coldest three-day stretch since Feb. 5-7, 2007, and it's going to give that one a run for its cold cash.
But the cold, which is a certainty, may be upstaged during the next few days what is shaping up as a monster storm -- at least virtually.
Computer models continue to show the potential for an East Coast blockbuster Tuesday into Wednesday, and if the model runs stay reasonably consistent, watch out for a threat big enough to set off the requisite panic-shopping stampedes.
One look at the trees this morning -- and we can't recall a January that was as generous with aesthetically pleasing winter storms -- indictated that the overnight snow was a bit soggier than expected.
As we posted yesterday, those 2 to 4 and 3 to 5 estimates were contingent on the snow-liquid ratios coming in at about 12- or 15-to-1. That would be 1.2 to 1.5 inches of snow for each 0.10 inch of precipitation.
The liquid amounts were reasonably close to the 0.25 forecast of yesterday afternoon, but the snow amounts from east and south of Center City didn't work out.
So much for the January thaw. Temperatures yesterday and Tuesday finished above normal for the first time since right after the new year, but that could be about it for the warmth this month.
Recall that the pre-season consensus was that with La Nina cooling conditions in the equatorial Pacific, winter would get off to a chilly start and then moderate in January.
But Accu-Weather's long-range forecaster Joe Bastardi says this month has taken cold turns he had anticipated, and given the strength of the La Nina -- it was solidly in "strong" category as of Monday -- "there is nothing like this in history."
You may have noticed that some of the region's snow-accumulation forecasts have a range big enough to drive a plow truck through.
Of course, this has something do to with the region's complicated topography and the science of trying to determine precisely just how much a given storm will develop.
But it's also very much tied to the vagaries of the snow-to-liquid ratios. Computer models now are seeing about 0.25 inches of liquid being squeezed out of this storm in the immediate Philadelphia area.
Tony Wood has been writing about the atmosphere for The Inquirer for 26 years. E-mail Tony here. And read all his columns here.
