Dreaming of a white Christmas? Snowy scene could be in the cards

cpassant@centredaily.comDecember 21, 2012 

Dreaming of a white Christmas?

The odds of tearing open the shutters and throwing up the sash to find new-fallen snow on Christmas morning aren’t exactly great in Centre County — but they’re not out of the question either.

Residents will see snow and even minor accumulations leading up to the big day and more in days following.

Just before dawn on Friday, overnight rain is expected to turn to heavy, wet snow, and the National Weather Service has issued a winter weather advisory through 7 p.m. Saturday for much of northern Pennsylvania and through the central mountains. Total accumulation is expected to be from 3 to 6 inches. Overnight lows will be in the mid to upper 20s.

A winter weather advisory for snow means that a significant amount of snow is forecast and will make for dangerous travel, according to the National Weather Service.

“There is going to be a system moving in to the Plains states late in the week and early next week, so it really becomes a timing issue,” said AccuWeather meteorologist Tom Kines. “Snow is definitely not out of the question Monday night or Tuesday, Christmas Day. The chances aren’t zero by any stretch.”

The storm dumped more than a foot of snow in some areas of the Midwest, canceled scores of flights and caused a deadly 25-car wreck in Iowa in blizzard conditions, according to The Associated Press. The giant storm system is expected to move through the Midwest and into the Northeast through the weekend.

Sunday and Monday in the region will remain cold with highs in the mid-30s and times of sun and clouds. Much the same is forecast for Christmas Day. But more cold weather is predicted Dec. 26 through Dec. 28, with snow, sleet and freezing rain. Lows on Dec. 27 and 28 will be in the teens.

Highs for December generally are in the mid-30s and lows in the low 20s, according to City Data, which collects information from more than 4,000 reporting weather stations.

“So far, our temperatures for this month have been about 7 degrees above normal,” Kines said. “But definitely the trend for the rest of the month is going to be closer to or even below normal, highs in the mid 30s and lows in the 20s.”

Typically, however, Centre County receives a modest amount of snow each winter, on average. December in Centre County averages about 8 to 9 inches of snow, Kines said. As of today, there have been trace amounts. On average, the county receives about 38 inches of snow for the entire winter, according to USA.com. Pennsylvania, on average, receives about 35 inches. Likewise, on average, the county sees nearly 10 days in December in which an inch or more of snow is actually on the ground.

But for it to snow here, it takes a certain formula.

“As far as central Pennsylvania is concerned, it all comes down to where our storms are coming from,” Kines said. “Our best snows come from the south, and the storms bring with them a lot of precipitation.”

Meteorologists are predicting an active storm season — above average — that could yield some major snow throughout the Northeast. The Mid-Atlantic into the Northeast has seen some consistency in tracking — or phasing — with storms. That could present more frequent storms. The recipe for snowstorms, however, doesn’t just depend on an active storm season; cold air is needed as well.

We’re starting to get in to a pattern where we are getting some storms coming up from the south,” Kines said. “Once we get into next week and the week after, we’re going to have closer calls with snow, meaning the potential is there for accumulation. It’s a matter of weather the cold air can hang on.”

Centre County’s geography has a good deal to do with it, too, Kines said. Westerly winds are bad. Easterly or northeasterly are good.

“Winds come down off the ridges from the west, and it’s sinking air — not a good ingredient for moisture,” he said. “Our best scenario for winter storms is when you get an east or northeast wind — which is actually rising from the Atlantic sea level to about 1,200 feet.”

When the air rises from the east, it brings with it precipitation off the ocean. However, in December, the ocean water is still warm. That’s not generally as big a factor later in the year, when the ocean’s temperatures drop and stay cold.

So, a white Christmas? Looks like there’s a chance. How about skiing? That depends on many factors.

Tom Matalavage, who has been working at Tussey Mountain for 26 years and blowing snow with the winter operations team for about 17 of those years, said he’s hoping to be able to blow enough snow to open right around Christmas or soon after.

“It’s still not as cold as I’d like it, but hopefully we’ll be able to start making snow on Saturday night,” Matalavage said. “At this point, we’d like to get open here by the Christmas break.”

The winter crews tested the snowmaking equipment earlier this month and are ready to go.

The formula for blowing snow all depends on what’s called a wet bulb, which is determined by air temperature, humidity and dew point.

“We need a wet bulb of 23 degrees,” Matalavage said. “It’s a combination of humidity, temperature and dew point, and we combine those things to figure out what the wet bulb temperature is. Above 25, we can’t make snow.”

By this weekend, the forecast temperature drops could yield a string of cold nights and possibly continue into January.

“The good news is that once we get into the Christmas date, we’re starting to see temperatures more to our liking,” Matalavage said. “I’d like to see daytime temps below freezing for 24 hours.

“But, were shooting opening around Christmas, realistically with tubing shortly after that.”

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