FLX flooding recap, weather forecast for the rest of the week.

finger lakes weather forecast wednesday august 15 2018 sun clouds showers flash flooding tuesday august 14 2018
Wednesday will have a welcome break in the weather for the flood-weary Finger Lakes. [Photo by Meteorologist Drew Montreuil]

Mostly Dry Until Late Thursday Afternoon

The Finger Lakes is getting a needed break in the rain as Tuesday’s low pressure system has finally departed the region.

So far, Wednesday has been a nice day. The morning fog has burned off and a pleasant mix of sun and clouds will develop for this afternoon.

There could be one or two isolated, light rain showers that pop up, but most areas will not see rain. Any rain that does fall will not cause additional flooding.

Temperatures will be in the mid 80s across the north with low 80s further south.

Thursday will start off in a similar fashion, but already a new weather system is eyeing the region. Showers and thunderstorms will pop up during the second half of Thursday afternoon as the first impacts of this system move into the region. The chances for rain will start in the southwest and will spread northeast through the late afternoon.

Thursday evening, showers will continue and could transition into a steadier rain after 10 pm.

Most of this rain should be light to moderate, but a couple heavier downpours are not out of the question. Widespread and significant flooding like Tuesday is not expected, but a few localized areas could see some minor flooding, as it will not take much rain to start causing problems in the wake of yesterday’s deluges.

Steady rain should taper off before dawn Friday, but an approaching cold front may trigger some additional late morning and early afternoon showers and storms. There will be a better chance for storms, some strong, over eastern New York.

A shower or two may linger into early Saturday before a nice, quiet weekend.

finger lakes weather flash flooding august 14 2018 seneca county southern tier rochester
Flood advisories and warnings from Monday and Tuesday, August 13-14, 2018 are shown in the green polygons. Flooding and heavy rain reports are represented by the blue wave icons.

Flood Forecast Analysis

Predicting flash flooding is a bit like looking for a needle in a haystack. There are so many variables to consider, from where storms will develop to how fast they will move, how recent rainfall will impact runoff, to the influences of terrain and urbanization.

This year, I’ve been trying to identify zones most prone to flooding similar to how severe thunderstorms are typically forecast. I’ve even been using the same 5-level classification scale for flooding as I have been with thunderstorms for several years.

finger lakes weather forecast flash flood map august 13 2018 august 14 2018
The first flash flood risk map, created shortly after 7 am Monday morning. Click to enlarge.

In anticipation of this event Monday morning, I posted my first flood risk map. I placed a Level 4- HIGH risk area across the Southern Tier, where heavy rain had recently fallen and flash flooding would occur with the least amount of additional rain. Concern over a larger area of heavy rain prompted Level 3 and Level 2 areas. The differentiation between these two zones was based on how much rain would be needed for flooding. Less rain would be necessary for flooding in Tompkins and Cortland County, for example, than in Seneca County. A broader area of Level 1- MINIMAL risk extended as far as the eastern suburbs of Rochester, where it would take truly significant rain to cause flooding on a more localized scale.

By Tuesday morning, when my second map came out, the destructive flooding in Seneca County was ongoing, prompting the use of the Level 5- EXTREME category, which I have never used in any situation before. Level 4 risk extended south from there and expanded across the Southern Tier. My third map, Tuesday afternoon, scaled back the threat for additional flooding and focused on the northeastern Finger Lakes and Central New York area with a Level 3- ELEVATED risk.

Given the evolution of the event, I am very pleased with the forecasts and how the zone-based approach worked.

From the getgo, the Southern Tier was expected to experience Flash Flooding with the Level 4 classification. Plotting all the flood advisories and warnings issued in that area results in a jumbled mess of green polygons. Flooding was commonplace and destructive. These exact areas were identified 24-36 hours in advance.

finger lakes weather forecast tuesday august 14 2018 flash flooding live weather updates
The second flash flood map, created at 7 am Tuesday morning. Flash flooding was already occurring in the Extreme Risk area. Click to enlarge.

Where the Seneca County floods occurred was on the edge of Level 2/3 risk in the first map I issued nearly 24 hours before the flooding. Had even half of the rain that fell there fallen 15-20 miles east over Tompkins County, similar impacts would have been felt.

The final area of flooding in our region was in a small area on the east side of Rochester. Flooding here was not as serious as in Seneca County and on a smaller scale. Rainfall reports over 6 inches accompanied this flooding. Again, had that magnitude of rain fallen in a higher risk area, destruction on par with Hector and Lodi would have occurred.

Whether flash flooding or severe thunderstorms and tornadoes, summer-time weather risks are often very localized events. The science of meteorology is far from being able to pinpoint where exactly severe thunderstorms or flooding will develop. With a localized knowledge of the area, a wealth of forecasting experience, and a healthy understanding of forecast model strengths and weaknesses, I would say that we can do a fairly decent job in raising the alarm when it is needed.

That is good news for everyone.

Your Support Matters!

Yesterday, I was able to provide constant coverage of the flash flooding from early in the morning well into the afternoon. In all, I posted on my live blog nearly 60 times throughout the duration of the event.

This would not have been possible without the generous support of donors and especially those who have contributed with monthly pledges.

At the beginning of July, I was able to leave my over-half time job to focus on building Finger Lakes Weather and to be available for updates when severe weather strikes. Normally, I would have been working a full 8 hour day on a Tuesday.

Because of your generous support, I was able to dedicate myself to weather forecasting yesterday. I have received many words of thanks and appreciation for my work, but I would like to pass that onto my donors and sponsors. Thank you so much for your support!

I do still have some gaps in my month-to-month finances, though, that need to be sealed up with additional donations or sponsorships. FLXweather.com had nearly 11,000 page views yesterday alone. Local businesses can tap into this captive audience with a sponsorship ad.

Please consider a monthly donation using the form below, or place an ad for your business on Finger Lakes Weather. Thank you for your continued support of Local Weather!

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.

2 Responses

  1. John Jay

    Should I cancel plans to visit the Binghamton area this weekend, Friday 8/17-Sat 8/18? Based on your flood maps for Mon 8/13 into Tues 8/14, it looks like Binghamton is in the bull’s eye! Are conditions expected to improve by this Friday, 8/17?

    • Meteorologist Drew Montreuil

      These maps were made for the threat through Tuesday 8/14. There is no flooding threat now, though rivers remain high and the Susquehanna at Vestal is still above flood stage. The weekend weather will be fine so there is no reason to cancel your trip.