Wednesday morning update on multi-round thunderstorm potential

Multiple rounds of thunderstorms are likely today across the Finger Lakes, including the chance for severe thunderstorms and flash flooding. Uncertainties remain given the very complex set up, but there is certainly a chance for some intense weather, particularly late this afternoon and this evening.

Active Weather Updates

Severe Thunderstorm Warning [Canandaigua, Geneseo, Dansville, surrounding areas]
Update Type:
Expires: September 2, 2026 9:45 am

Severe Thunderstorm Warning [Rochester, Greece, Irondequoit, surrounding areas]
Update Type:
Expires: September 2, 2026 9:15 am

Therefore, I am skipping the normal morning extended forecast in lieu of a more specialized update focusing in on the latest expectations for today as of 8 AM this morning. I will likely have additional updates later in the day, which will automatically show up in a box within this post, as will any warnings that are issued throughout the day.

Thunderstorm Set Up

Our region resides in the battle ground between hot and humid air to the southwest and cooler air to the northeast. This boundary has remained over the area for the last couple of days and is often referred to as a “Ring of Fire” due to the train of thunderstorm producing weather systems that travel along it.

So far, the disturbances we have seen have been on the weaker side or have not coincided with prime thunderstorm conditions. That very well may change today with a pair of disturbances passing through a very supportive environment.

The second of these will have the potential to be especially potent, coming late today and interacting with warm, very moist air and strong wind fields aloft. More on that below.

Round 1: This Morning

An area of severe thunderstorms is moving into western New York and northwest Pennsylvania early this morning. Several severe thunderstorm warnings and even a tornado warning were in effect as of 8 AM.

The atmosphere ahead of these storms over the Finger Lakes is marginally supportive of thunderstorms, but this cluster is expected to eventually weaken as it heads east. How quickly this happens is an unknown, but there is at least some severe threat across our area this morning. The further west, the higher that chance will be. Damaging winds will be the primary threat.

Most weather models this morning are doing a poor job resolving this storm complex, with many not even showing it at all. Those that do show it indicate it should be exiting the area before noon.

This first round will have two potential influences on the second round later today.

First, the atmosphere will need time to recover behind the stabilizing effects of the rain and cloud cover. This is expected to happen quickly, even if sunshine is limited this afternoon due to high levels of humidity and favorable temperature profiles throughout the different layers of the atmosphere.

Second, thunderstorms can leave behind subtle boundaries and wind shifts that later storms can ingest, leading to supercell structures and an increased threat for all modes of severe weather, including tornadoes. These boundaries are usually far too subtle for any modeling to pick up on and can be almost invisible to observational data. They are a true wildcard in forecasting what may come next.

Round 2: Late Afternoon/Evening

In the radar graphic at the top of this post, you will see in the far top left another small cluster of storms entering northern Michigan off Lake Michigan. This is indicative of the second disturbance, which should arrive in our region by this evening.

Those thunderstorms should persist this morning as they cross Michigan and Lake Huron, then increase this afternoon over Ontario, Canada. A turn to the southeast is expected as well, following in the path of Round 1, coming into our area.

There are a couple of possibilities as this happens.

First, there may be an area of new thunderstorm development ahead of these storms over the Finger Lakes region. If this happens, we can expect storm initiation in the 3-5 PM window, with storms started as isolated supercells then combing into line segments after 5 PM. All modes of severe weather would be possible, including large hail and tornadoes. Additional, weaker storms would then be likely as the disturbance arrives during the evening hours, with the main threat transitioning to localized flash flooding from repeated heavy rain.

Another possibility is that the disturbance itself is the main event, arriving during the early evening as a line of widespread storms with damaging winds and localized flash flooding.

These two are obviously the more concerning scenarios, but there are lesser scenarios that could unfold as well.

If the atmosphere does not recover sufficiently, or if the main energy from this disturbances passes by outside the region, then showers and storms would be less likely to reach intense levels. There would likely still be showers and storms, and most areas should see at least some rain no matter what during this window… but a significant severe weather event is not a certainty at this point.

Action Steps

The weather will need to be monitored today, especially during the next couple of hours and again during the late afternoon and evening hours.

This is a high uncertainty but high potential set up. If everything comes together, it could be the biggest event of the year. But it also may not align, ending up as a more modest or non-event.

Warnings should always be taken seriously, but especially today. Thunderstorms have the potential to become particularly intense. Remember that severe thunderstorms can produce tornadoes with little warning, and that severe thunderstorm winds can be as destructive as a tornado: it matters little if the wind is coming straight or spiraling. Therefore, severe thunderstorm warnings should not be ignored simply because they are issued often.

If a flash flooding threat develops, it will mostly occur after dark. It can be especially difficult to gauge the severity of flood waters at night. Never drive through flood waters, and have an action plan in place if you are in a flood prone area. The flooding threat is less of a concern than the thunderstorm threat, but this message bears repeating anyway.

All warnings will automatically be listed on this blog post and the FLX Weather homepage. Any minor updates I have will also show up in the same area. I may have a live blog later today depending on the storm evolution and timing.

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