‘Heavy rain,’ wind gusts to 50 mph possible into early Thursday. Snowflakes on Friday?

What may well become the region’s heftiest rainfall in over three months evidently is a virtual certainty Wednesday night into early Thursday.

As much as 1.5 inches — which surpass the total amount of rain that has fallen since Aug. 18 — could land in the official rain gauge at Philadelphia International Airport, said Alex Staarmann, meteorologist at the National Weather Service Office in Mount Holly. Up to 2 inches is possible north of the city, he said.

To the north, a foot of snow could top the higher elevations of the Poconos, where a winter storm watch is in effect.

The weather service also added a wind advisory for the entire Philadelphia region from 10 p.m. to 4 a.m. for gusts up to 50 mph.

As you likely will be hearing again during the next several weeks, it won’t come close to washing out rain deficits and drought anxieties, but the atmosphere is hinting that it may be ready to behave very differently.

It’s even possible that a light accumulation of snow coats areas to the north and west of the city on Friday, with flake sightings as far south as Philadelphia “possible,” said Staarmann.

“A pattern change is definitely on the way,” said Joe DeSilva, a meteorologist with the National Weather Service office in Mount Holly.

In its Wednesday outlook, the National Oceanic and Atmospheric Administration’s Climate Prediction Center had the odds favoring below normal temperatures for most of the United States for the Nov. 28-to-Dec. 4 period. It also had the chances titled for above-normal precipitation in the Philadelphia region and in much of the rest of the nation.

In ordinary times, that’s a question reserved for snow, but after having broken a 150-year-old record for consecutive days without measurable rain and making a run at a a record-dry fall, a forecast of 1 to 1.5 inches of rain qualifies as news.

“Heavy rain” — and when is the last time you saw that phrase — is due to start late Wednesday night and continue into the early-morning hours, the weather service says.

Then another round of rain is expected Thursday night, with rain possibly mixing with wet snow — even in the city — Friday morning.

Since Aug. 18, Philadelphia had received 0.88 inches of rain through Tuesday, according to NOAA’s Middle Atlantic River Forecast Center, which uses a sampling of county stations. That’s about 11 inches below long-term averages, or 7% of normal.

The figures for the surrounding counties are pathetically similar. The interagency U.S. Drought Monitor has the entire region in “severe drought” and parts of southeastern New Jersey in “extreme drought.”

Both New Jersey and Pennsylvania have posted drought advisories.

Philly has a shot at all-time records for any three-calendar-month period, 2.37 inches, set from Sept. 1 to Nov. 30 in 1922.

The weather service says heavy wet snow is possible in the Poconos, with a winter storm watch up for areas above the 1,500-foot level, with the potent storm due to settle across the Northeast and Mid-Atlantic.

The storm will generate wintry northwest and west winds Thursday and Friday, perhaps gusting to 40 mph, with temperatures in the region no higher than the mid-40s Friday. Rain and snow showers are possible north and west of the city, with a coating possible, with a chance that renegade soggy flakes could invade the city, the weather service says.

After a remarkable run of sunny, warm and dry days, the atmosphere appears to be flipping into late-autumn mode, meteorologists say.

The colder weather is sharpening the temperature contrasts that energize the storm-moving winds, said Dave Dombek, senior meteorologist with AccuWeather Inc.

”It’s finally happening,” he said. “We’re not just talking drought, drought, drought. We’re actually talking about some other stuff going on.”