Significant snow event clips FLX from the south Wednesday Night

Details Unclear on Tight Snow Gradient

High pressure will pass north of the Finger Lakes today and park itself north of New England as a large, powerful storm system develops along the Mid-Atlantic coast tomorrow.

There is an area of snow showers in the area Tuesday morning from lake effect thanks to chilly northwest winds over the Great Lakes. Within the broader area of snow showers, there is a narrow band of heavier snow, just a couple miles wide at most, traveling south through southern Cayuga and Cortland counties.

Some roads may be on the slick side with a light coating of snow. Locally up to an inch may fall this morning as the lake effect very gradually shifts southwest and weakens.

A few breaks of sun may show up late in the day, but for the most part, it will remain cloudy today. Temperatures will not move much, sticking in the mid and upper 20s that are already in place.

New clouds will stream in from the south overnight and thicken on Wednesday as the winter storm begins to take shape. Snow will move in from the south during the hours near and just after sunset tomorrow.

The most intense snowfall will occur between roughly 9 PM and 6 AM Wednesday night-Thursday morning. Areas further south will have heavier snow for a longer duration, while areas to the north will see light snow throughout the event.

A band of very heavy snow with snowfall rates of over 2 inches per hour will probably just stay south of the NY-PA state line, but 1 inch per hour rates could make it as far north as central Steuben, southern Schuyler, southern Tompkins, and extreme southern Cortland counties.

Unfortunately, since we are on the tight northern edge of this system, our snow amounts are extremely sensitive to slight variations in the track. A shift of a mere 20-30 miles further north could double many of the snow amounts shown above.

On Sunday, I shared a plot I was making to track the 51 European model ensemble members, grouping the expected snow amounts into five categories. I have now tabulated data for 17 runs of the ensembles, and no category has ever had more than 45% of the members for a given run in it.

There is little run-to-run consistency. For example, three runs ago, Ithaca had its lowest chances for a foot or more, with just 12% of the ensembles showing that. Two runs later, and the most recent version, Ithaca has its greatest chance for over a foot at 41% of ensemble members.

As much as I desire to make one single snow map for a given event, the forecast confidence is low enough that a second map may be necessary. I am publishing this map now to give as much lead time as possible.

The map I have created lies close to, but slightly higher than what could be considered a middle of the road approach. Again, though, a shift of 25 miles, which is a mere wobble on the large scale, could significantly change the map.
The European ensembles continue to show wide variations in possible snow amounts, in this case for Ithaca. The lack of an overall trend and inability for a single category to emerge as an overwhelming favorite is the result of the razor-thin difference between a major and minor snow event.

Snow Aftermath

The main impacts from this system will be felt early Thursday morning. Before the sun rises, snow will still be falling for most areas and travel will be difficult. The further south, the worse road conditions will be.

Snow should quickly pull out after sunrise, and by the late morning, sunshine will be increasing. Travel conditions should vastly improve with few worries on the main roads by midday. Secondary and rural roads will improve through the afternoon as road crews and the sunshine clean up.

Temperatures on Thursday will stick to the mid and upper 20s where a thick snowpack exists, but from about the northern tips of the lakes to the shore of Lake Ontario, highs should be near or just above 30.

Friday will be sunny with similar high temperatures. Morning lows, however, will be quite cold across the snowy southern half of the region. Isolated pockets could fall into the single digits with widespread teens elsewhere.

Clouds will increase on Saturday with a few showers or flurries late. These may extend into Sunday with a new batch Monday into Tuesday. Temperatures during this time period will range through the 30s and into the low 40s.

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