Look back at the 1991 March ice storm: What are the odds something like this happens again?

Weather Blog

ROCHESTER, N.Y. (WROC) — 30 years ago Wednesday, a devastating ice storm wrecked havoc on Rochester and the surrounding area, leaving behind a memory forever imprinted into the minds of those who lived through it.

Residents went to bed that Sunday evening the 3rd, and woke up Monday morning to trees, vehicles, and other exposed surfaces coated in over an inch of ice, downed power lines and trees leaving thousands without power, and over $170 million in damages by the storm’s end.

Atmospheric Set Up

The dynamics and overall set up behind this system were unique, and it takes a very specific set of atmospheric conditions to produce such an extended period of freezing rain.

On the morning of March 3rd, a developing low pressure system made its way from the Gulf of Mexico northward towards the Carolinas.

Meanwhile Western New York the day prior just finished seeing decent warmth for March with temperatures in the 50s, before a trough pushed through sending temperatures back down below freezing.

A front continued to sit nearby providing those not too far to our south with above freezing temperatures ahead of the approaching low to our south.

To our north, a large area of high pressure sat over Canada and provided winds that came out of the north and east from Sunday all the way to Monday morning.

This set up is crucial in providing not only enough cold air, but a layer of cold air shallow enough so as not to refreeze falling raindrops into less sinister sleet.

06Z Monday Surface Anlaysis

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What’s interesting here is that despite these cold, northeasterly winds temperatures at the surface started to warm from Sunday afternoon into Monday morning from the 20s to just below the freezing mark, likely due to the warm air moving in aloft from the approaching low to pass just to our south and east.

15Z Monday Surface Analysis

At first glance, this doesn’t perfectly represent a strong signal that would call for a big ice storm, especially at the caliber that ended up playing out. The location of the low pressure as it traveled across New England appeared too far to the east to support enough warm air for freezing rain, but Rochester happened to fall in the “sweet spot” of prime atmospheric conditions. A narrow and shallow enough cold layer funneling in at the surface along with enough warm air above the surface was enough to keep precipitation to fall as rain, and form ice on every surface it touched. Freezing rain fell for about 17 hours beginning as early as Sunday afternoon and lasting all through Monday morning. Plus, areas slightly west of Rochester saw an additional 4-6″ of heavy, wet snow adding to the wintry mix.

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Notice how a total of 1.22″ of precipitation fell on Monday, March 4th in Rochester, and 0.5″ of that fell as snow. This means over an inch of freezing rain fell on just that day alone. Also, temperatures from Sunday night into Monday morning started in the upper 20s and slowly warmed to the freezing mark. Getting freezing rain to accumulate is much easier the colder the temperatures are at the surface, and the farther away from 32° they are. It’s remarkable how temperatures were only so much below 32°, and yet we managed to get over an inch of ice to accumulate so quickly and steadily.

What’s going on at the surface doesn’t tell the whole story, especially when it comes to freezing rain. A big player in why this event played out the way it did was the above freezing air not too far above the surface, and why this event will be remembered for years to come.

Could something like this happen again?

Is it possible to get an ice event like this again in the future? I’d say it’s certainly possible, but getting the precise conditions required for icing to this extent is something you don’t see too often at all. It may also just be a matter of time before something similar happens again, but this time perhaps we’ll know what to expect.

~Meteorologist Christine Gregory

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