Afternoon thunderstorms raise flash flood concerns

Torrential Downpours Possible Tuesday Afternoon

A small disturbance clipped the northern Finger Lakes this morning with a few showers.

While innocent enough on its own, this disturbance is setting up the risk for flash flooding across the southeastern Finger Lakes this afternoon.

While the disturbance itself will be long gone by this afternoon, it will leave behind subtle boundaries in the atmosphere that will serve as a focal point for thunderstorms later.

Before that happens though, temperatures and humidity will spike. By the early afternoon, most of the region will be above 85 degrees with a few places hitting 90 degrees. Dewpoints will climb into the upper 60s and low 70s as tropical moisture associated with what is left of Hurricane Barry seeps into the area.

Thunderstorms should begin to develop along the aforementioned west-east boundaries by 2 pm this afternoon as a second disturbance approaches. While severe weather is generally not expected, any thunderstorms will be capable of producing torrential downpours.

I have issued a Level 2- Low flash flood risk across the areas most likely to see thunderstorms this afternoon. This is shown in yellow in the attached map. The flood threat could exceed Level 2 status if multiple storm cells move over the same area repeatedly. While the chances are low, this could result in isolated moderate to even significant flooding. Gorges and other areas of steep terrain, and urban areas will be especially prone to flooding.

Thunderstorms will quickly dissipate as the sun sets this evening. It will be a warm and muggy night with overnight temperatures hovering near 70 degrees. Some nighttime fog is likely in areas that see thunderstorms this afternoon.

More Widespread Rain Wednesday

Tropical moisture from Barry will continue to move into the Finger Lakes overnight and into Wednesday. A series of disturbances will move through as well, tapping into the moisture with rounds of rain and thunderstorms.

One batch of rain and thunderstorms will move through during the early morning hours. This rain will focus on the northern half of the region. Locally heavy downpours will be possible, especially on the southern edge of this area of rain.

A second area of rain and thunder will arrive during the early afternoon. This rain should be more widespread across the Finger Lakes. Depending on how the atmosphere reacts to the first batch will determine how heavy the second batch becomes.

A third round will be possible during the evening, this time focusing back over the southern half of the region and the Southern Tier in particular. The threat for heavy rain and repeated cells will exist. If an area sees heavy rain today and gets hit hard again tomorrow, there could be significant flooding concerns.

Overall, the flood risk Wednesday will be at least a Level 1- Minimal across the entire area. The risk level could go as high as Level 4 for portions of the Southern Tier depending on how today unfolds and how the second and third rounds of rain evolve tomorrow.

With the clouds and rain Wednesday, temperatures will sit in the mid and upper 70s.

The chances for rain will decrease on Thursday with just a few morning showers. Afternoon thunderstorms will be possible Friday, Saturday, and especially Sunday.

Temperatures will return to the 80s on Thursday and will push 90 degrees Friday. Saturday could be the hottest day yet this summer with widespread 90s and heat index values pushing 100 degrees. The heat will break on Sunday with temperatures next week mostly in the 70s.

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