Tri-state temperatures this week are going on a roller-coaster ride, starting Tuesday, which will be sunny, with a daytime high just two degrees short of 60, forecasters said.
"These temperatures are about five degrees below normal for the middle of November, the National Weather Service in Upton said. A west wind should top out at 11 mph.
The cloud-clearing high pressure system creating the metropolitan area’s autumn day allows the daytime heat to easily escape the Earth’s surface once the sun goes down.
Tonight, various frost advisories prevail for southern Nassau, and the Hudson, Bronx and Manhattan Counties – only Staten Island merited a freeze warning -- as the night time low falls to 32 degrees, the weather service said.
Wednesday’s daytime high zooms up to 56, aided by mostly clear skies -- and an arriving warm front, according to the National Weather Service.
The departing high pressure system, with its falling, drying air, heads out to the Atlantic, as the same kind of pattern develops higher in the atmosphere, the forecasters said.
A complicating factor is a warm front destined for the metropolitan area that is tied to a storm-causing low pressure system in southern Canada.
As a result, "Winds become southerly and moisture begins to increase. Highs will be right around normal."
Flowing up from the South, those breezes again will not exceed 11 mph – but what a difference their direction makes in Wednesday night's temperatures.
For starters, not only are there not frost or freezes predicted, but "Given the moist southerly flow, lows Wednesday night don`t make it below the 50s in the NYC metro area and not below 40 elsewhere," the weather service said.
And those breezes again on Thursday push the highs into the mid-60s – and possibly upper 60s, readings the weather service called "well above average."
The average mid-November temperature is 42, according to records for Islip begun in 1963.
Both a cold front and then a low pressure system, with rising, warm air that can condense into rain drops, develop high in the atmosphere.
On Thursday, "Showers can start as early as the afternoon hours for far western locations, but most of the rain will happen overnight," the weather service said, predicting a quarter of an inch may fall.
Friday’s chances of rain are 50% before 1 p.m. or so as an upper- and a lower-level low pressure system, or a trough, sweeps through on Friday "that will reinforce the cold air across the region."
"With the trough, Friday morning could have a few light rain or snow showers," the weather service said. Two years ago, trace amounts of snow also fell before Thanksgiving.
The winds then shift, and will blow from the northwest, so wave goodbye to the warm weather.
At least another high pressure system should give tri-staters a lovely, clear though chilly weekend – starting Friday night.
That is when, the weather service said, "Lows plummet into the 20s across much of the region with NYC mostly in a 30 to 36 degree range."
The winds then ease, but Saturday still will be cooler than usual, with a high around 49 – before thermometers begin trending up again, once again with breezes originating in the South.
"Then on Sunday, with a continuation and increase of the southerly flow as high pressure moves farther offshore, a warmer day is expected with highs more in the low to mid 50s," the weather service said.
Sunday looks like a cloudy day with a high near 54.
Rain and possible snow showers might arrive Sunday night and linger into Monday as a storm-causing low pressure system sails into the Ohio and Tennessee Valley.
The concern, forecasters said, is their models suggest that "somewhere within the Northeast," a strong cyclogenesis" or a storm or even cyclone might form.
After all, a rare seven tornadoes – four on Long Island and three in Connecticut touched down last weekend.
Still, there is, the forecasters said, "A lot of uncertainty in the forecast Sunday night and thereafter so forecast has low confidence."