Lake Ontario - Open Waters from Mexico Bay to the St Lawrence River Marine Forecast
| This Afternoon...South Winds 10 Knots Or Less Becoming North. Waves 1 Foot Or Less. |
| Tonight...Northeast Winds 10 Knots Or Less Becoming South. Waves 1 Foot Or Less. |
| Tuesday...Southeast Winds 5 To 15 Knots. A Chance Of Showers In The Afternoon. Waves 2 Feet Or Less. |
| Tuesday Night...Southeast Winds 10 To 15 Knots. A Chance Of Showers. Waves 1 To 2 Feet. |
| Wednesday...Southeast Winds 10 To 15 Knots. A Chance Of Showers. Waves 1 To 3 Feet. |
| Thursday...Southeast Winds 5 To 15 Knots. A Chance Of Showers. Waves 2 Feet Or Less. |
| Friday...South Winds 10 To 15 Knots. Showers Likely. Waves 1 To 3 Feet. |
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Area Forecast Discussion National Weather Service Buffalo NY 1121am EDT Monday May 12 2025 Synopsis High pressure will slide southeast off southern New England coast this afternoon, with a southerly return flow bringing much warmer air into the area and dry weather continuing through the remainder of the day. A broad diffuse area of low pressure and moisture will then spread northward across the Ohio Valley and Great Lakes. This will bring a chance of a few showers starting Tuesday and lasting through the end of the week, but there will be plenty of dry time built in as well. Near Term - Through Tuesday Surface high pressure will slide off the southern New England coast this afternoon, with a southerly return flow of much warmer air pumping northward across most of western and north-central NY. A light gradient flow will for lake breeze formation with a weak onshore flow developing this afternoon. High temperatures will be in the mid 70s to low 80s across most of the area, with cooler readings found closer to the lakeshores. Tonight will be a transition period with showers entering the western Southern Tier late tonight. An upper level trough will move across the Pacific Northwest and aide in dislodging a broad upper level trough across the Mississippi and Tennessee Valleys. Further, a broad area of moisture will advance northward and enter western NY tonight. Initially, clouds will thicken and produce overcast skies across the forecast area. A tight moisture gradient and isentropic lift along an exiting mid-level ridge axis will advance light rain showers into the western Southern Tier late tonight. There is uncertainty as to how far north these showers make it overnight. If they do advance into the Buffalo metro and Finger Lakes region they will likely encounter more low-level dry air and be in the form of isolated showers and sprinkles. Dry conditions will continue from the northern Finger Lakes to the eastern Lake Ontario region. The combination of clouds and showers will limit cooling tonight, with lows in the upper 50s to low 60s. Deeper moisture will advance northward across most of the forecast area as the upper low moves into the Ohio Valley Tuesday. 850mb moisture transport will advect anomalously high PWATs (Precipitable Waters) into the northern Mid-Atlantic region . While we might not tap into the core of the highest PWATS, forecast amounts are still above the 90% percentile for mid-May across western NY. There is uncertainty in the location of upstream precipitation and the potential for embedded shortwave troughs. Daytime heating and deep moisture underneath the trough will increase instability Tuesday. Scattered to potentially numerous showers are possible across western NY, however confidence is low in coverage and location. A few thunderstorms can't be ruled out Tuesday afternoon. The upper level ridge axis will persist across eastern New York into New England and keep low chances of showers across Jefferson and Lewis counties Tuesday. A steady south-southeast wind will allow areas that were on the cooler side Monday, such as near the Lakes, to reach the 70s, and the low 80s across the Saint Lawrence Valley Tuesday. Cooler across the higher terrain east of Lake Erie with highs in the 60s. Short Term - Tuesday Night Through Wednesday Night A mid level closed low over the lower Ohio Valley Tuesday evening will move very slowly northeast, gradually opening up into a negatively tilted trough that will deamplify with time as it moves across the Great Lakes. A moist airmass will remain in place through the middle of the week, with surface dewpoints well into the 50s and possibly lower 60s at times. Weak shortwaves will traverse through the larger scale mid level trough, with each one providing a periodic increase in large scale ascent, with more localized low level forcing from lake breeze boundaries and terrain driven circulations. The weak forcing and moisture will maintain a chance of showers at times through the middle of the week, but there will be plenty of rain free time as well. Temperatures will remain warm through the middle of the week, running 5-10 degrees above average for mid May. Long Term - Thursday Through Sunday The weakening, slow moving trough that reaches the Great Lakes during the middle of the week will linger Thursday, then drift towards New England Friday. Weak forcing associated with the trough, moisture, and diurnal instability will support a chance of a few showers and isolated thunderstorms Thursday with uneven/spotty coverage. Friday, a mid level closed low is forecast to move into the upper Great Lakes, then move slowly east across Ontario and Quebec next weekend. A warm, moist, and somewhat unstable airmass will remain in place Friday ahead of this next system, maintaining the chance of a few scattered showers and thunderstorms. A cold front associated with the mid level system will cross the eastern Great Lakes Saturday, with another round of showers and thunderstorms possible. Sunday, the mid level trough will become established from the Great Lakes into New England, with a cooler post-frontal airmass advecting into the area. Lingering moisture and forcing from the trough will support a chance of a few more showers. Marine High pressure draped across southern New England will drift off the east coast through tonight. Expect mainly light southerly offshore flow through tonight, although weak gradient flow will allow for an onshore flow to develop on both lakes this afternoon through early evening. Tuesday through Thursday, winds will generally be east to southeast on the lakes with a light to moderate chop at times, but no Small Craft Advisory conditions are expected through the week. There is a low chance of thunderstorms during this time. NOAA Buffalo NY Office: Watches - Warnings - Advisories NY...None. Marine None. |
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