Ice jam flooding, severe winter storm threaten Finger Lakes

Warm, Rainy Weather Brings Flood Threat

A very active weather pattern is evolving over the Finger Lakes for the next few days, bringing a variety of significant threats to the region.

The first threat will be flooding.

Temperatures are on the rise across the Finger Lakes with many places already into the 40s Thursday morning.

High temperatures Thursday afternoon should push into the upper 40s and 50s and remain in that range through the overnight and into Friday.

After a few morning showers, most of the daytime hours should be relatively dry today.

However, an area of rain is expected to develop tonight as tropical moisture works its way north.

Extreme amounts of moisture, on the order of 500% of what is normal for January, will push into the Finger Lakes, resulting in locally heavy rain tonight into Friday.

There is still some uncertainty on where the heaviest rain sets up, but it should be somewhere near or over the Finger Lakes.

Rainfall amounts over an inch are possible within the band of heaviest rain.

Combined with the snowmelt, significant rises are expected on small streams and even larger rivers, many of which are still ice covered.

As the ice breaks up, it can get caught on river banks and bridge supports, causing a jam to form. Rapid rises in water then occur upstream until the dam breaks, when rapid rises downstream occur.

In addition to the ice jam threat, small streams and basement flooding will also be possible, especially in the localized corridor of heaviest rain.

Severe Winter Storm Unfolds

It is becoming increasingly likely that a severe winter storm will impact the Finger Lakes, beginning mere hours after temperatures are in the 50s Friday afternoon.

A strong cold front will move from northwest to southeast through the Finger Lakes Friday afternoon, quickly sending temperatures from the 50s into the 20s and 30s.

At the same time, a strong low pressure system will move across Pennsylvania and into New England, spreading very heavy precipitation back into the Finger Lakes, starting late Friday afternoon.

At first, there will be enough warm air aloft to cause a period of freezing rain. A quick glazing of ice is likely for most areas, with more significant ice accumulations possible across the eastern Finger Lakes into Central New York.

Freezing rain will turn to heavy snow Friday night, again from northwest to southeast. At some point, the transition to snow will slow down and stop, likely over Central New York.

For much of the Finger Lakes though, a prolonged period of very heavy snow is likely Friday night through Saturday morning. Snow will linger into Saturday afternoon, especially over the eastern Finger Lakes as the storm system pulls away.

Snow totals remain quite uncertain due to sensitivities to storm strength and the transition of ice to snow. However, despite the low confidence, I am starting to see enough consistency to at least take a stab at snow totals.

An area of 16-24″ is possible near Lake Ontario and into the northwestern half of the Finger Lakes. Widespread amounts of a foot or more are possible.

The snow totals on the northwest edge of the system, back towards Buffalo, and especially over the eastern Finger Lakes are extremely uncertain.

Remember, areas that see LESS snow will see MORE ice, so the threat for severe winter weather exists all across the area.

Travel will be extremely difficult all across the region on Saturday and should be discouraged.

Cold temperatures and areas of lake effect snow showers are likely behind this system Sunday into Monday. High temperatures on Sunday will struggle to reach 10 degrees with wind chills below zero.