A few showers as chilly air continues to be reinforced

finger lakes weather forecast wednesday september 29 2021 sun clouds cool air lake effect showers
A few showers will pop up this afternoon and increase tonight as cold air crosses Lake Ontario. [Photo by Gwen Moshier]

Chilly and Unsettled

September is coming to end on a colder note thanks to a large dip in the jet stream around low pressure over eastern Canada.

Small waves of atmospheric energy are riding along the jet stream aloft, helping to reinforce our supply of cool air on northwesterly winds.

Given that these are mostly weak, moisture starved disturbances, the chances for rain will be limited to scattered showers enhanced by Lake Ontario.

The first showers to pop up will be this afternoon. These will remain quite isolated and most areas will not see rain during the daytime hours. Skies will be a mix of sun and clouds, but most of the sunshine will be through the morning.

Northwest winds will blow at around 10 mph with occasional gusts over 25 mph. High temperatures will mostly range from 60-65 degrees, with mid 60s most likely across the northern half of the region.

Tonight, shower activity should increase as conditions for lake effect improve. On and off showers are likely through the night. Some steadier light rain may end up developing for Wayne, Ontario, Seneca, and Yates counties.

Throughout the northern Finger Lakes, overnight temperatures will stick close to or just above 50 degrees thanks to the lake effect. On the fringes of the region, and especially across southern Allegany and Steuben counties, and possibly Cortland County, mid 40s are more likely.

Thursday will be quite cloudy. Only some occasional breaks of sun will poke through the overcast. Showers will decrease compared to the nighttime hours but are unlikely to completely disappear.

North-northwest winds will be a bit lighter than today, but temperatures will be colder. Only a few isolated locations along I-90 will manage to hit 60 degrees. Higher elevations will end up around 55 degrees, with the rest of the region spread between these two endpoints.

finger lakes weather 7-day forecast wednesday september 29 2021
This graphic represents an average over the entire Finger Lakes region. Localized variations should be expected. Click to enlarge.

Increasing Temperatures…and Rain Chances

The weather pattern will begin to break down and shift Thursday night. Winds will drop and become more westerly. This will cut off our supply of lake induced showers and cloud cover. Skies will gradually clear, and temperatures will drop in response.

By Friday morning, widespread 40s and pockets of 30s are likely in the region. Sheltered valleys of the Southern Tier and possibly Central New York could see a little frost. Closer to the lakes, lows will be between 45-50 degrees.

Clouds will again develop once the sun rises and starts to heat the ground thanks to the remains of cold air overhead. The clouds will become thick from the late morning through the mid-afternoon, but will break up later in the day.

Most areas will climb back into the low 60s, though areas east of Cayuga Lake may struggle to get much beyond 60 degrees. Higher elevations in this area will likely stick to the upper 50s.

Winds will turn definitively to the south and southwest Friday night. Overnight temperatures will be split with low 50s throughout the north and mid and upper 40s to the south. Daytime highs Saturday will be more uniform with all the region comfortably between 70-75 degrees.

Saturday will start sunny, but thin clouds will build in during the morning. These will become thicker through the afternoon and into the evening. No rain is expected, though.

Saturday night will be much warmer thanks to the clouds and south winds with widespread mid and upper 50s. The first rain showers will arrive in the hours leading up to dawn Sunday.

On and off showers are likely throughout Sunday. A couple afternoon rumbles of thunder may even be possible. It does not look like a complete washout of a day, though. High temperatures should be generally around 70 degrees.

The weather system responsible for the rain on Sunday will stick around for Monday as well. Monday looks rainier than Sunday, with a few thunderstorms once again possible.

The weather will remain unsettled for much of next week as the weather pattern gets stuck. Tuesday and Wednesday look to have just some scattered showers with perhaps a better chance for rain Thursday and Friday. The details this far out are sketchy, though, so be sure to monitor the forecast coming up.

More Information:

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finger lakes weather 7-day forecast wednesday september 29 2021
This graphic represents an average over the entire Finger Lakes region. Localized variations should be expected.

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Follow Meteorologist Drew Montreuil:
Meteorologist Drew Montreuil has been forecasting the weather in the Finger Lakes region since 2006 and has degrees in meteorology from SUNY Oswego (B.S. with Honors) and Cornell (M.S.). Drew and his wife have four young boys. When not working or playing with the boys, he is probably out for a run through the countryside.