A dry and comfortable Saturday will open the weekend across the Finger Lakes and Central New York, with filtered sunshine and temperatures reaching the mid-60s to low 70s before clouds thicken later in the day.
Rain will spread into the region overnight and continue through much of Sunday, according to the National Weather Service offices in Buffalo and Binghamton. The system could produce locally heavy rain, especially toward the Southern Tier, but the threat for flash flooding remains low.
Dry weather holds through Saturday
High pressure centered over eastern Ontario will keep Saturday dry across the region. Mid- and high-level clouds moving in from the west will dim the sunshine at times, especially later in the day, but no daytime rain is expected.
Temperatures will begin the morning mainly in the 40s and lower 50s, then climb into the mid-60s to low 70s during the afternoon. Rochester is forecast to reach about 66 degrees, with highs near 67 in Geneva and Penn Yan, 69 in Syracuse and Elmira, and 71 in Ithaca.
Light winds and low humidity will accompany the mild afternoon. Winds will gradually turn from the northeast toward the east and southeast as high pressure moves away and the next low-pressure system approaches from the west.
Clouds will become more widespread from southwest to northeast during the afternoon and evening. Even so, outdoor conditions should remain dry through Saturday evening in most communities.
Neither weather service office had watches, warnings or advisories posted for New York early Saturday.
Rain develops after midnight
The first showers are expected to reach the western Southern Tier and southwestern Finger Lakes late Saturday night, then expand northeast toward Rochester, Geneva and Syracuse during the early morning hours Sunday.
Most locations should remain dry until after midnight. Current forecasts bring the chance of rain into Rochester and Geneva after about 1 a.m., while steadier rain is expected to reach Ithaca, Elmira and Syracuse closer to or after 2 a.m. The exact arrival time will depend on how quickly moisture spreads ahead of the low.
Overnight temperatures will generally settle into the lower and mid-50s. Increasing clouds and a light east to southeast wind will limit the temperature drop compared with Friday night.
The arriving air mass will contain unusually high moisture for mid-September. That moisture, combined with broad lift around the approaching system, will support a long period of rain rather than a brief line of showers.
Sunday turns cool and rainy
Rain will become widespread before or around daybreak Sunday and continue through much of the day. The steadiest rain is expected from the morning into the afternoon before the system begins shifting east later Sunday and Sunday evening.
Clouds and rain will hold temperatures down. Highs are forecast near 63 in Syracuse, 65 in Ithaca and Penn Yan, and 66 in Rochester and Geneva. Elmira could reach the upper 60s, although temperatures there will depend on the track of the low and the timing of the heaviest rain.
Rainfall amounts will vary across the region. Much of the Finger Lakes and Central New York is expected to receive roughly a half-inch to an inch, while totals of 1 to 1.5 inches are more likely closer to the New York-Pennsylvania border. Localized amounts above that range are possible where heavier showers persist.
The highest totals are most likely across the Twin Tiers and areas farther southeast, but confidence remains limited in the exact placement of that corridor. The projected track of the low has shifted somewhat north, and another small change would move the heaviest rain with it.
The weather service identifies locally heavy rain as the primary concern because of the deep moisture feeding the system. Ponding could develop in urban and poor-drainage areas, but widespread flash flooding is not expected. Recent rain has left soil moisture somewhat higher near the Twin Tiers, while parts of north-central New York remain abnormally dry.
The chance for thunderstorms is low. Forecast guidance shows little or no instability north of the Pennsylvania border, making Sunday primarily a steady-rain event across the Finger Lakes and Central New York. A few rumbles of thunder remain possible closer to northeastern Pennsylvania or the western Southern Tier.
Rain should taper from west to east late Sunday afternoon and evening. Low clouds and patches of fog may linger over higher terrain after the steadier rain ends, while overnight lows fall into the mid-40s to around 50.
A brief break arrives Monday
Cooler and drier air will move south behind the departing system Sunday night. High pressure building from eastern Canada should bring a mainly dry Monday, although clouds may remain stubborn and a passing shower cannot be completely ruled out near the Pennsylvania border or Catskills.
Monday will feel distinctly cooler, with highs mainly in the lower to mid-60s. Rochester and Penn Yan are forecast near 60, while Geneva, Elmira, Ithaca and Syracuse should reach the lower or middle 60s. A northeast breeze could become noticeable in western parts of the region.
Some valley fog may develop early Monday where skies partially clear after Sunday's rain. Otherwise, the day should feature a mix of clouds and occasional sunshine before more moisture begins gathering to the south and west.
Cool, unsettled pattern continues next week
Forecast confidence decreases from Tuesday through Thursday as high pressure over eastern Canada competes with an upper-level low near the Great Lakes and developing low pressure along the Mid-Atlantic coast.
That pattern could send several rounds of showers toward the region, but the northern extent and timing of each round remain uncertain. Areas closer to the Southern Tier currently have the better chance for rain Tuesday, while another round may spread farther north later Wednesday or Thursday.
The extended outlook favors fall-like temperatures even during the dry intervals. Daytime highs should stay mainly in the 50s and 60s, with overnight lows in the 30s and 40s. The coolest nighttime readings are most likely in sheltered valleys and northern portions of Central New York.
Autumn officially begins at 8:04 p.m. Tuesday, and the broader weather pattern will match the change in season. Clouds and intermittent showers are expected to remain more common than prolonged sunshine through the middle of the week, although continuous rain is not anticipated.
Check the latest forecast at the FingerLakes1.com Weather Center.
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