The weather over the next 48 hours will be rather active across the Finger Lakes as a number of systems pass through the area.
A storm system over the Midwest extends well east into the Mid-Atlantic and Southeast states early Tuesday. A warm front will lift north towards our region, increasing the shower activity gradually through Tuesday morning and afternoon.
The warm front itself may never make it into the Finger Lakes, as temperatures will only rise modestly during the day Tuesday from morning temperatures near 40 degrees into the mid and maybe upper 40s. The warm air will remain in place overnight, with temperatures steady in the mid 40s throughout the nighttime hours.
Rain will become more widespread tonight as colder air slowly works its way east. The Finger Lakes should see a solid 6 to 9 hours of steady, mostly light rain from the late evening hours into early Wednesday morning. The rain should come to an end as the front passes by, and much of Wednesday morning and early afternoon will be dry.
Temperatures will start to drop, however, with most places entering into the 30s by the late afternoon. Overnight temperatures on Wednesday will be somewhere in the low, mid or upper 30s, depending on location and geographical features. This is where the forecast confidence begins to break down.
By Wednesday evening, the cold front from earlier in the day will be just to our east. Low pressure will then develop along the front and spread precipitation back into the Finger Lakes starting later Wednesday afternoon. Initially, this precipitation should be all rain, but as temperatures continue to drop, at least some areas may start to mix with snow. Precipitation will continue into Thursday, with some enhancement from the Great Lakes.
How much snow mixes in, and whether or not the precipitation is able to turn to all snow, is a very sensitive process where even a change in temperature of a degree or two can have a large impact.
The most likely scenario at this point in time is for mostly rain across the Finger Lakes, with some snow mixing in at times, especially over higher elevations. Some minor accumulations may be possible, especially in the higher terrain of the eastern Finger Lakes. I would say this scenario, or a warmer, all rain scenario, has a 75% chance of occurring.
The other scenario, however, cannot be dismissed and remains on the table. Though less likely, if enough cold air moves in quick enough, most of the region could see a change over to snow with some minor accumulations on the order of an inch, with slightly more in the higher elevations. A quicker change over could result in slightly higher snow totals. In a coldest case scenario with the most snow, the region could see a few inches. This coldest case scenario is very unlikely, but is still worth mentioning.
Regardless, precipitation will ease up on Thursday as high pressure builds in. Temperatures will struggle to reach 40 degrees on Thursday, but should be back in the mid 40s on Friday and could push 50 degrees on Sunday.