ITHACA, N.Y. — If you live in a low-lying area, it’s time to check that your storm drains are cleared and your sump pumps are working. A Flash Flood Watch has been issued for Tompkins County from 8 PM tonight through 12 PM tomorrow.

Observational data shows that since the start of the month, the Ithaca-Tompkins Airport has picked up near four inches of rain, which is more than a month’s worth, and most of that has fallen in just the past few days. The ground is saturated and its ability to hold more rainwater is severely limited.

Unfortunately, a storm system over the Mississippi River Valley is sending waves of moisture and moderate to heavy rain into Upstate New York. An expansive high pressure system stretching from Bermuda northward into Atlantic Canada is effectively blocking the system from moving eastward, so the system can only very slowly work its way north-northeastward to get around the hump that is the strong jet stream ridge of high pressure to its east. This slow movement will allow for successive waves of heavy rain, including some embedded strong thunderstorms, to penetrate into the Northeast today and tomorrow.

Unlike a regular flood, flash floods are often more dangerous because they occur with little warning, often developing within minutes of a heavy rain. The heavy rain may be further upstream from the affected area, so do not assume that because the rain is light at your house that there is no risk. The quick nature of flash floods makes them much more powerful than regular floods, and they often become raging torrents of water, sweeping away everything in their path.

Low-lying areas with poor drainage (Fall Creek, West End, Southwest Ithaca, valley areas) will be most at risk from a flood, as well as homes and businesses adjacent to creeks and streams. Keep an eye on the television or carry your cell phone in case a flash flood warning is issued for your area, and be prepared to leave for higher ground if necessary.

If you are out driving and come across a flooded road, do not attempt to cross it and find an alternative route. Even shallow water can damage and/or disable your vehicle, and floodwaters can rise very quickly. It only takes 6″ of fast-flowing water to wash a vehicle off a road. When traveling, give yourself extra space between other drivers and drive at a reduced speed due to the risk of hydroplaning over standing water. If driving at night, use your low beams.

Keep an eye out for flash flood warnings and further updates from the National Weather Service Binghamton forecast office. The regular weekly weather forecast will be issued tomorrow morning.

Brian Crandall

Brian Crandall reports on housing and development for the Ithaca Voice. He can be reached at bcrandall@ithacavoice.com.