We are now less than a day away from a high impact storm system to move through the region Friday and the holiday weekend. Here are some of the impacts we expect.
THURSDAY: Low pressure is starting to crank up to our west, the early stages of a deepening storm. A surge of moisture will arrive later in the day as warmer air starts to pump northward. While an initial wintry mix could fall across higher elevations southeast of Rochester, the bulk of this activity quickly changes to all rain and continues into Thursday night. A few slick spots perhaps across high terrain, but nothing wintry will fall otherwise. Travel both by car and plane westward toward places like Chicago start to get dicey into Thursday night. Locally, we stay all rain into the night.
IMPACT: VERY LOW

FRIDAY: A rapid transition from rain to snow happens late morning. Temperatures will knife downward fast, likely dropping below freezing in the span of just a few hours. This will open the window to “flash freeze” potential where all that prior rain doesn’t have enough time to evaporate, turning to ice. Strengthening winds (to 60+ mph) will accompany this cold air, further aiding in the abrupt deterioration of road conditions. Any leftover moisture will turn rain over to snow with a few inches possible. Regardless how how much or how little falls, it will blow around and cause visibility issues. Flash freezes have a tendency to catch people off guard. Westward travel toward places like Cleveland and Chicago will be difficult. Current thinking suggests earlier in the morning is better if moving around the Rochester area Friday. After that cold front gets here, it’s downhill quickly.
IMPACT: HIGH
SATURDAY: This is where precise track of the low starts coming more into play. Leftover synoptic moisture is likely to be limited, but scattered snow showers and bitterly cold air will be locked in place. Heavy lake-effect snow will fall from the Lake Erie shoreline to Western Monroe County. Temperatures likely won’t get out of the teens Saturday either, so any roads that still have yet to be treated could feature residual icy spots. For any travel stops or just for pumping gas, remember to bundle up as well when out of the car. Wind chills will be near or below zero fairly easily, even just a few minutes outside can be troublesome at these levels.
IMPACT: MOD

CHRISTMAS DAY: Aside from an isolated snow shower or two, the day is otherwise quiet. Temperatures will have a hard time topping 20 degrees, marking one of Rochester’s coldest Christmas Day’s (in terms of high temperatures) in more than 20 years. Travel should be fine in town but still difficult west heading into the lake effect snow band. IMPACT: LOW