A flood watch is in effect for Long Island through Tuesday morning, as the area faces an average of 11/2 inches of rain -- with higher amounts possible in isolated spots, the National Weather Service said.
Thanks to drier air working its way aloft, the forecast rain amount was adjusted slightly downward, said Joe Pollina, weather service meteorologist based in Upton. As of around 4 p.m., Islip had recorded 0.67 inches and Centereach, 0.5 inches, he said.
An approaching warm front is bringing with it "widespread moderate to heavy rainfall" at times during the watch period, the service said.
That's on top of a deluge Friday into early Saturday that dumped 6.13 inches in Old Bethpage, 5.9 inches in Wantagh and 5.65 inches in Centereach.
That drenching storm flooded major roads across Long Island during Friday night's commute, stranding some motorists and turning low-lying areas into temporary lakes.
Rain is likely to come in "batches," with one early Monday afternoon, as heavy rain moves in from just south of the Island, said Brian Ciemnecki, meteorologist with the National Weather Service based in Upton.
After a possible short break, expect rain or showers, especially after 3 p.m., he said, with "pockets of moderate to locally heavier rainfall" into the late evening. Temperatures are forecast to be in the low 70s.
As of late afternoon, some arrivals into LaGuardia Airport were experiencing weather-related delays of an average of just over an hour, with some arrivals at Kennedy delayed an average of two hours, according to the Federal Aviation Administration's website. A few departures from LaGuardia, Kennedy and Long Island MacArthur airports were facing delays, and the FAA advises travelers to check with their airlines.
Rainfall during the watch period may result "in flooding of small streams and rivers along with urban and poor drainage" areas, the weather service said.
Given the amount of rainfall Friday into Saturday, "the ground is quite saturated," Ciemnecki said, and areas prone to flooding will "be pretty quick to flood again."
The 4.58 inches of rain officially recorded for that time frame in Islip, makes the month "on track to rival the wettest June on record," said Tim Morrin, also a weather service meteorologist in Upton.
Already, based on 4.92 inches that fell in the first nine days, it's the third wettest June, compared to that same time frame for 2000, which recorded 5.25 inches, and 2003, which recorded 5.95 inches. Holding the record for the entire month, based on data kept since 1985, is 2003, which recorded a total of 10.80 inches of rain for the month, he said.
Looking at daily records, the official 4.15 inches that fell in Islip on Friday "smashed" the previous record of 1.27 inches that fell on that day in 2006, he said.
As for Tuesday, with temperatures in the upper 70s, expect more showers in the morning and possibly a thunderstorm, as well as decreasing rain and a chance to "dry out a little more toward afternoon," Ciemnecki said. The following days, too, are expected to be "unsettled" with the threat of rain, he said.
The flood watch "means there is a potential for flooding based on current forecasts," the service said.
Long Islanders are urged to "monitor later forecasts and be alert for possible flood warnings," the forecasters said.