Monitoring flash flood risk closely for southeastern Finger Lakes

finger lakes weather forecast monday august 13 2018 flash flooding meteorologist drew montreuil
The potential for flash flooding will need to be watched closely through Tuesday, especially for the southeastern Finger Lakes and Southern Tier. [Photo by Meteorologist Drew Montreuil]

Excessive Rain Possible, But Not Certain

The potential for heavy rain will exist across portions of the Finger Lakes through Tuesday, but flooding is not a sure bet at this time.

The weather system in play today is a large low pressure system in the upper levels of the atmosphere that has separated from the jet stream. Without the support of the upper level winds to carry the low on, it is just slowly meandering around the region. Monday morning, the low was centered over southwestern Pennsylvania.

To the east of the low, copious amounts of atmospheric moisture are present, leading to widespread heavy rain across eastern and central Pennsylvania. These rains are moving very little and will likely produce another round of catastrophic flooding for areas that have already seen devastating floods in recent weeks.

Some of this rain is attempting to push north into the eastern Finger Lakes but is having trouble penetrating our region. The main uncertainty in the forecast is how the rain evolves over the Finger Lakes today.

finger lakes weather forecast flash flood map august 13 2018 august 14 2018
The primary concern for flash flooding will be over the southeastern Finger Lakes, where moderate to heavy rain will be possible on Monday and again Tuesday morning. [Click to enlarge.]
The most likely scenario is for a wave of rain to push north later this morning and early afternoon. Locally heavy rain will be possible across Chemung, Tompkins, Tioga, and Cortland County.  There are some scenarios on the models where rain persists well into the afternoon with a couple of inches possibly falling. Further north, the rain is less likely to be excessive.

The rain today could set the stage for a more serious flood threat Tuesday morning. A similar set up to what is over Pennsylvania this morning could unfold across the eastern half of the Finger Lakes as the low meanders northeast.

On its own, this rain, should it occur, would be capable of producing flash flooding. However, if rain also falls today, flooding will occur quicker and more seriously.

For this reason, I have placed the southeastern Finger Lakes in the Level 3- Enhanced category on my flood map through Tuesday morning. A small area of high risk exists across the Southern Tier where flooding has occurred as recently as late last week.

Should moderate to heavy rain make it further north today and the threat for heavy rain tomorrow increases in confidence, that high risk area could need an expansion.

This is a situation to closely monitor. Please consider subscribing to this blog to receive immediate email notification of new posts.

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Flash Flood Threat Ends Wednesday

The threat for heavy rain will diminish Tuesday night as the low slowly tracks overhead and then to the east.

Scattered showers will continue to be possible Tuesday night with one or two stray showers also possible on Wednesday.

Thursday looks like it will start out dry and sunny, but some scattered afternoon thunderstorms may be possible. These seem most likely over the southwestern Finger Lakes at this time.

Friday will have a better chance for showers and thunderstorms as a cold front moves through the region.

Temperatures ahead of this front will rise into the middle 80s Wednesday, Thursday, and early Friday.

Humidity will remain high during this time, with daily dewpoints continuing to hover in the upper 60s and low 70s.

Finger Lakes Weather Radar

After some bugs in the radar page that arose from changes Google made to their Google Maps platform, the radar has been fixed and appears to be stable.

You can access the radar page by clicking the image below. The radar is fully interactive and mobile friendly.

finger lakes interactive weather radar
Click the banner to go to the radar page!
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.