LAKE EFFECT STORM "GALILEO"

December 22-23, 2002

Maximum Snowfall: Lk. Erie: 7" (Wales); Lk. Ontario: 24" (Castorland).

Duration: 30 Hours +/_

Prime Feature: Lightning and Thunder east of Lake Ontario, very windy through the period causing severe driving problems.

Lake Flake Scale: ** 2 Flakes

Just in time to add a coat of fresh snow to the region after a mild thaw, lake effect storm Galileo caused some pretty rough driving problems. The event did not produce tremendous snowfall east of Lake Erie, but it did produce significant driving problems especially south of the city. There were numerous accidents on the morning of the 23^rd and the Buffalo Skyway was even closed for a period of time. Off Lake Ontario, it took a little longer to get things fired up, but when it did the snow came hard and fast. During the evening of the 23^rd snowfall rates as high as 5 inches an hour were accompanied by thunder and lightning.

The event began on the 22^nd as a deep low pressure system set up just to the south and east of James Bay Canada. This is a prime position to produce single banded storms off Lakes Erie and Ontario. On the 22nd the air did not get quite cold enough aloft to produce the degree of instability necessary for heavy lake snows. If it would have been a couple of degrees colder, then areas east of Lake Erie would have been much harder hit. Eventually however the air did get colder and on the 23^rd the winds were very strong, gusting in excess of 40 mph at times. Because they were directed right up the longest fetch of Lake Erie, they drove the snow far inland, all the way across the Rochester region and even farther east. Off Lake Ontario the snows really fired up late in the day on the 23^rd as a secondary short wave dropped southeast from Ontario across the region. The short wave deepened and moistened the unstable layer over the lake which greatly intensified the snowband. Highmarket’s observer had reported snowfall rates of 5+ inches an hour with thunder and lightning during the evening. Fortunately, the short wave moved through rather quickly and after midnight a strong subsidence inversion developed, squashing what was left of the deep convective lake effect clouds.

One of the other interesting points about this storm was the nature of the snow flakes during the event. Off Lake Erie the snow at times consisted of white pellets that were as big as 1/4 inch in diameter. They often fell in very heavy showers, then would change over briefly to large flakes. The temperature structure of the atmosphere was responsible for this type of snow. It is also with this type of snow that we will often get reports of lightning and thunder.

Overall...the event was not a major storm. However, the brief burst of heavy snow east of Lake Ontario, the existence of lightning and thunder, and the strong winds that produced numerous traffic accidents in blowing and drifting snow all contributed to making this storm a 2 flake (**) event.

Here are some representative amounts (these include frontal snow as well)....

Off Lake Erie

Off Lake Ontario