Rochester, N.Y. – If you lived through it, you will probably never forget it. It is the great ice storm of March 1991.  Most folks consider this to be the worst, most devastating storm to ever affect Rochester on a large scale in modern history.

Thirty four years ago on March 3 and 4, there was storm so severe it would crippled the electrical infrastructure.  As a result, a state of emergency was declared for 19 counties, including the city of Rochester.  I was a very young meteorologist at the time and I found it difficult to understand what triggered a storm of this magnitude. But I soon learned the simplest explanation was an alignment of weather ingredients that was essentially stuck in one position. That repetitive, long-lasting natural event completely shut down Rochester.

The set-up was an arctic airmass coming in from the north and a lot of warm, moist air moving in from the south.  This creates a condition in meteorology known as overrunning. The overrunning situation occurs when warm air rising over the top of much colder air at the surface.  This can happen anytime of the year, but in winter icy precipitation usually transitions from snow, sleet to freezing rain. In this instance, the precipitation did not change.  It was a persistent freezing rain for more than 17 hours, creating a glaze or layer of ice ranging from three quarters of an inch to two inches. Over 10,000 trees were severely damaged – just in the city. Over 200,000 homes and businesses were without power, some for over two weeks. The amount of cleanup was immense. 

The rarity of this storm is illustrated when examining the climatological history of Rochester.  Statistically, the ice storm of 1991 is considered a 100-year storm.