The long Fourth of July weekend is wrapping up with a much different weather pattern than the one that started it: cooler air, thick clouds, slow-moving storms and a growing concern for heavy rain across parts of the Finger Lakes and Central New York.
Sunday will mark the beginning of an unsettled stretch as a slow-moving upper-level trough and weak low pressure system move across the region, according to the National Weather Service. The setup will keep showers and thunderstorms in the forecast through Monday night, with some storms capable of producing torrential downpours, gusty winds and isolated flash flooding.
Today’s weather
Sunday will start gray and damp in many areas, with patches of fog and low clouds lingering through mid-morning. Conditions should improve somewhat after sunrise, but the break will not last long.
As daytime heating increases, scattered showers and thunderstorms are expected to develop during the afternoon and evening. The highest rain chances will be across the Southern Tier, Twin Tiers, southern Finger Lakes and areas closer to the New York-Pennsylvania border, though parts of Central New York could still see showers or storms.
The main issue Sunday is not widespread severe weather. It is storm motion.
Winds aloft will be weak, meaning thunderstorms will drift slowly. Some could stall, repeatedly move over the same locations, or become anchored near terrain. That raises the risk for localized heavy rainfall in a short period of time.
The Weather Service says storms may produce efficient downpours because of deep moisture in the atmosphere. Precipitable water values will run near 2 inches in some areas, which is a strong signal that any storm could produce heavy rain quickly.
The day will feel humid, especially from the Twin Tiers south into northeast Pennsylvania, where dew points may climb into the low and mid-70s. Farther north, including areas closer to the New York State Thruway, the air will be somewhat less humid and rain chances will be lower.
Highs will range from the upper 70s to mid-80s across much of the region.
Heavy rain threat continues into Monday
The heaviest and most persistent rain threat will likely continue Sunday night into Monday, especially south and southeast of Binghamton, across northeast Pennsylvania and into Sullivan County. However, the broader Finger Lakes region will remain close enough to the system for periods of rain and embedded thunderstorms.
The Weather Service says some areas could see stripes of very heavy rain overnight Sunday into Monday as low pressure helps organize showers and storms. Exactly where that happens remains uncertain, but the pattern favors localized flooding where storms repeatedly track over the same communities.
Monday will not look or feel like a typical July day. A cool easterly flow will take hold, keeping temperatures mainly in the 60s and low 70s for much of the day in areas with steadier rain. Clouds will dominate, and periods of rain will continue.
The Buffalo forecast office says the most persistent rain Monday will likely fall across the Southern Tier and Finger Lakes, while areas farther north toward Lake Ontario may see fewer showers. Still, occasional rain could reach the south shore of Lake Ontario at times.
The Binghamton forecast office says rainfall totals of 2 to 3 inches are possible in parts of northeast Pennsylvania and the southern Catskills, with locally higher totals possible. While those highest totals may stay south and east of the heart of the Finger Lakes, the pattern bears watching across Steuben, Schuyler, Chemung, Tompkins and nearby counties.
New York Heat Wave Breaks Nighttime Temperature Record as Extreme Heat Continues Across the City A flood watch may eventually be needed if confidence increases in where the heaviest rain will set up.
Midweek outlook
The upper-level trough will not completely leave the region on Tuesday, but the steadiest rain should begin shifting east as the low pressure system pulls away.
That means Tuesday will stay unsettled, but not as wet for everyone. Expect mostly cloudy skies with scattered showers and a few isolated thunderstorms, mainly across the Southern Tier and Finger Lakes.
Temperatures will remain on the cooler side for July, with highs generally in the 70s.
By Wednesday, the forecast improves. Most areas should turn mainly dry, aside from a stray pop-up shower. Skies should become partly to mostly sunny, and temperatures will climb back toward more seasonable levels.
Highs Wednesday are expected to reach the upper 70s to mid-80s, bringing a more typical summer feel back to the Finger Lakes and Central New York.
Warmth and humidity return late week
The quieter midweek pattern will not last long.
Thursday is expected to be the warmest day of the week as the region settles into a flatter west-to-east flow pattern. Highs should push well into the 80s, and humidity will increase again.
Late Thursday, another disturbance approaching from the Great Lakes will bring the next chance for showers and thunderstorms. Timing remains uncertain, but the pattern points toward another round of unsettled weather Thursday night into Friday.
Friday will likely stay warm and humid until the next front moves through. Showers and thunderstorms are possible again, though it is too early to know whether any stronger storms or heavy rain threat will develop.
Next weekend remains less certain. Early guidance points to seasonable temperatures, with highs in the upper 70s to low 80s and only low chances for showers or thunderstorms.
For now, the biggest weather concern comes as the holiday weekend ends Sunday and the new workweek begins Monday. Anyone traveling, camping, boating, or cleaning up after Fourth of July activities should keep an eye on the radar, especially in areas that see repeated downpours.
Slow-moving storms will be the difference between a nuisance rain and a localized flooding problem.
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