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Environment & Science

Will there be snow to end the weekend? This, other upcoming storms, have to 'thread the needle'

SundayMondaystorm.jpg
TropicalTidbits.com
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This graphic shows a storm system that could impact the area and bring an inch or two of snow Sunday into Monday.

BETHLEHEM, Pa. — Just call it climate chaos.

Less than two weeks after the Lehigh Valley set a record coldest high temperature on Christmas Eve, it made a run at a record high.

Factoring in the wind chill, the “feels like” difference between the two days? Roughly 85 degrees.

Dec. 24 saw the mercury struggle to reach 13 degrees, but on Wednesday it soared to 63 — just 3 degrees shy of a record 66 for the date.

  • It's been a tremendously mild start to January, but it doesn't mean we won't have a shot at snow
  • Forecasters say upcoming storms will have to "thread the needle" but they're looking at snow chances over the next 10 days
  • Sunday into Monday could see a few inches of snow for the area

The swing has been so drastic that the Christmas freeze feels long ago and far away. Perhaps it’s because the start to January has felt more like the beginning of April.
Through the first five days of the month, the Allentown area is averaging a high of 47.5 degrees, a departure from normal of 16.5 degrees.

And even though the warmth has peaked and temperatures are sliding, long-range forecasts suggest our chances to build on December’s 1.4 inches of snow aren’t looking great.

Or are they?

Upcoming storm could line up just right

While the recent behavior of the atmosphere has been volatile, meteorologists say a tricky forecast has emerged for Sunday night into Monday.

A storm system expected to develop off the East Coast could bring a shot of snow for the Lehigh Valley, but things will have to play out just right.

That’s because the system is either going to set up east of North Carolina or somewhere farther north, off the coast of Virginia, the National Weather Service said.

Where that storm develops will have implications regarding how far north precipitation tracks, with a more northern track currently favored. That would bring a rain/snow mix near the Intersate 95 corridor and mostly snow to the Lehigh Valley area Sunday into Monday.

“Either way, this doesn’t look to be a very strong system,” the weather service said in its latest forecast discussion. “For that reason, even a ‘high end’ scenario would probably mean at most 1 to 2 inches of snow.”

Storms like this have to “thread the needle”

“A lot of people don’t understand what 'thread the needle' means,” EPAWA meteorologist Bobby Martrich said in his latest video forecast.

It involves a pattern, Martrich said, that lets precipitation and cold air meet at just the right time, “requiring ideal timing and track in an otherwise iffy background state.”

“What does that mean? It means the pattern is not very good right now,” Matrich said, pointing to the mild temperatures that kicked off the month.


READ: 'I would rather be right than be first': Meteorologists weigh in on the challenges of winter storm forecasting


But it doesn’t take a polar invasion of air like what we saw in December to make winter storms possible.

“This time of year, near-average [temperatures are] good enough to support snow,” he said. “You don’t need below-average temperatures in the middle of January to produce snow because it’s the coldest climatological period of the year.”

And it’s not just Sunday into Monday that forecasters are keeping an eye on.

There’s a winter storm signal for the following weekend that’s too early to get into any significant detail on. But if the storm emerges and manages to coincide with a transient cooler shot of air, things could get interesting.

Examining the model ensembles, Martrich said they’re still trying to reconcile what could happen but putting some “telling” information on the board at this early juncture.

“There is a considerable spread … but the fact that you have this many members northwest leaning of the mean … is very telling. That’s telling me we have to look out for a possible winter storm threat in a thread-the-needle fashion.”