Winter weather could return in Philly in mid-February, forecasters say

By the end of the month, the daylight hours will have increased by well over an hour, with 30% more sunshine. Some of the buds out there look as if they’re about ready to burst, the gloom of the last week notwithstanding.

After experiencing all of one week of winter, Philly’s latest snow drought entered Day 15 Saturday, and the snowpack across the country has shrunk in the last two weeks, according to data from the Rutgers University Snow Lab, with cold air once again on hiatus.

New York City has had all of 2.3 inches of snow for the season. Philly, at 8 inches, has had more snow than Minneapolis, which has recorded 7.3.

» READ MORE: Philly's snow drought ended emphatically in mid-January

The government’s Climate Prediction Center’s latest two-week outlook through Feb. 16 strongly favors above-normal temperatures from the Great Plains to the Atlantic Coast.

But the forecast issued Friday for the following two weeks takes a decidedly icy turn, with an Arctic pattern shift suggesting a possible “significant cold snap” in the central and Eastern United States,” the climate center says.

Perhaps “two or three” more snowfalls might happen into March in the Philly region, said Paul Pastelok, the long-range forecaster for AccuWeather Inc.

Those anxiously awaiting spring need not despair, however. Pastelok said it may turn out that Groundhog Phil will be at least half right in his call for an early spring. Pastelok isn’t seeing six more weeks of winter — but “maybe a three-week window.”

The first two months of the “meteorological winter,” which began Dec. 1, were prodigiously wet, with 13.83 inches of precipitation officially in Philly, making it the third-wettest December-January period in records dating to 1872. It finished behind only the 1978-79 and 1913-14 periods.

In keeping with the overall world-warming trends, the months also were quite mild, about 4 degrees Fahrenheit above the normals.

» READ MORE: Philly winters aren't what you think

But proving again that snow and cold don’t always correlate tidily, January’s 8 inches of snow were a few flakes above average in a month that saw the end of a record 716-day stretch without an inch of snow measured in Philly.

The El Niño warming of ocean waters in the tropical Pacific that has energized upper-air winds carrying weather to the United States has been a player all winter and that’s going to continue through March, said Brad Pugh, seasonal forecaster at the climate center.

Lately it has ratcheted up its influence, said AccuWeather’s Pastelok, energizing a southern storm track that has dumped rain on the Southeast, and California is in line for a deluge.

» READ MORE: El Nino's effects on U.S. weather are expected to persist through March

For now, at least, after more than 13 inches of precipitation in the last two months, the faucet over Philly has been turned off. “All the moisture is being robbed,” said Pastelok.

But El Niño hasn’t been the only player, as Pugh noted.

Upper-air patterns over the Arctic enabled the spillage of cold air into the contiguous United States in mid-January, as anyone who watched the NFL playoffs is aware. Temperatures were below zero when the Kansas City Chiefs hosted the Miami Dolphins, and blizzard conditions forced a postponement of the Pittsburgh Steelers-Bills game in Buffalo.

» READ MORE: Developments in the Arctic can export frigid air to the United States

Both the U.S. and European computer models foresee a major pattern change with high pressure building in the Pacific northwest in the second half of February, said Pugh.

Winds circulate clockwise around high pressure, so areas to the east of the center experience cold winds from the north and northwest.

“It looks stormy,” said Pastelok, “but how cold is the air going to be? There’s too much warm air building over the Northern Plains and central Canada, and the snowpack is eroding.”

Snow has a refrigerating effect on air masses that tend to moderate over bare ground. “If there’s no snow left on the ground, I don’t know how cold that air is going to be by the time it gets here.

“It makes it difficult for us here in the East to get any type of cold air masses.”

In addition, the polar vortex, the upper-air winds circling in the Arctic and containing frigid air, is swirling away up there. “The vortex looks to strengthen somewhat in early February,” NOAA researchers Amy Butler and Laura Ciasto said Tuesday on their climate.gov blog.

In five previous winters in the last 50 years that coincided with strong El Niños, late-season snowfall was boom-and-bust in Philly. Only a trace was measured for the rest of the winter after Feb. 1, 1973, 0.1 inches in 1998, and 4.6 in 2016.

In contrast, the post-Feb. 1 totals were 28.8 inches, in 1983; and 51.5, 2010. The normal Philadelphia snowfall after Feb. 1 is 12.3 inches.

As for this season, Pastelok said he is not ready to join a “winter’s over” chorus — yet.

“I think there’s a three-week window we still have left where we could have maybe two, maybe three, storms that could bring some snow here,” he said.

Phil, with no help from computer models, will have his say on Friday.