Meteorologists: Christmas weekend storm system 'once in a generation type of event'

Dec. 20—WATERTOWN — An "incredibly powerful" winter storm system also described by meteorologists as a "once in a generation type of event" is forecast to move through the area over the Christmas holiday weekend.

High winds, rain, snow and lake-effect snow accompanied by dramatically dropping temperatures are expected to impact the region starting Friday and continue through at least Sunday, Christmas Day.

Meteorologists with the National Weather Service in Buffalo said in a forecast discussion Tuesday that "Some of the parameters of this intense storm are climatologically 'off the charts,'" including the potential for record-setting low barometric pressures.

The service said the deepening low-pressure system moving into the area on Friday will "easily" meet the definition of a bombogenesis in which atmospheric pressure drops at least 24 millibars in 24 hours. The phenomenon, also known as a "bomb cyclone," is relatively rare in the lower Great Lakes, according to meteorologists.

After uneventful weather Wednesday, the service says conditions will begin to deteriorate late Thursday. Thursday's temperatures are expected to be in 40s, resulting in most precipitation falling that day as rain, although a wintry mix could be seen in some locations as temperatures begin to drop.

Temperatures Friday will then plummet as a low pressure system moves into the area from the Midwest, changing all precipitation to snow and producing very strong winds. The service says the combination of 40 mph to 50 mph winds and snow will result in blowing snow. Meteorologists noted that some of the strongest winds, which could produce scattered power outages, will occur in the Thousand Islands area.

Widespread snow will taper off late Friday, but the service says there is then a risk for a "prolonged" and "paralyzing" lake-effect snow event downwind from Lakes Erie and Ontario. With winds of as much as 50 mph, the service says blowing and drifting snow could result in "near zero" visibility in places.

On Saturday — Christmas Eve — the service says a deep southwesterly flow of very cold air will continue to support accumulating lake snows, mainly north of Buffalo and Watertown earlier in the day, but settling over the cities Saturday night. On Christmas Day, the lake bands are expected to continue, while moving south of the cities, with high temperatures in the teens and 20s and with 30 mph winds generating wind chill temperatures of 10 degrees above or 10 degrees below zero.

The service says cold temperatures will continue into Monday, although the risk of lake-effect snow will lessen.