Monday Night-Tuesday Morning Snow: Sunday updates

finger lakes weather forecast map showing four zones that have unique characteristics and expectations for snow Monday night and Tuesday morning, as explained further in the blog post text.
The Finger Lakes region will be on the northern edge of a winter storm Monday Night and Tuesday morning, leading to large variations snow amounts and high uncertainty in the fine details.

A quick moving but intense snow event will clip the Finger Lakes Monday night into Tuesday morning, but the forecast remains an especially tricky one.

Uncertainty remains high in the exact snow amounts, and there will be no exact snow amounts forecast in this blog post. Instead, I wish to highlight four zones across the Finger Lakes and the expectations and possibilities across those regions. I also wish to illustrate just why this system is especially difficult.

First, a few of the basics:

When:

Snow is not expected to arrive in the Finger Lakes region until near or after midnight Monday night. The snow will continue into Tuesday morning, but should mostly be over by noon. The Tuesday Morning commute will be highly impacted in some areas.

Overall Picture:

A quick moving low pressure will track across the Mid-Atlantic and quickly move offshore south of New England. The atmospheric set up is favorable for an intense band of snow to the north of the low. This band is expected to be relatively narrow. Dry air and less favorable dynamics just north of the band will lead to a very sharp cutoff in snow amounts on the northern edge.

finger lakes weather graph showing the high variations in snow amounts shown on the European model ensembles, as described further in the blog post text.
Model guidance is highly variable, decreasing its usefulness in this situation. Click to enlarge.

Source of Uncertainty:

Pinpointing where this band and cut-off will setup is a bit like walking a tightrope. One small shift in either direction and snow amounts may be drastically different. Unfortunately, the Finger Lakes region is positioned right in this zone where there will be large variations in snow amounts.

It is no surprise that the models are all over the place with snow amounts as a result. For those forecasts that simply feed model data directly to the public, or (slightly better) use a blend of model data, there will likely be wild fluctuations in the reported forecasts. Already I am heading comments as such.

Even the model ensembles, which take the same model and run it dozens of times with slightly different conditions and equations, are all over the place. Typically, 48 hours ahead of an event, there is at least a general trend to pick out on the ensembles. However, that is far from the case now.

In the overnight run of the European model ensembles, total snow amounts for Ithaca literally range from 0” to 14”. I took the 51 ensemble projections and broke them into bins at 3-inch intervals, with special bins for amounts under an inch and over 9.0 inches.

None of these five bins exceeded a 25% share of the ensemble members. The lowest percentage came in the middle bin of 3.1-6 inches. A whopping 22% showed less than an inch, while 16% showed over 9.0 inches.

In other words, the model guidance isn’t much of a guide this time.

Unfortunately, many forecasts stop there, spit out a number, and ignore the uncertainty. Not Finger Lakes Weather.

How I have been forecasting:

Throughout the end of the week, I have been mentioning this system in my blog post. I have consistently maintained that I felt the core of the heaviest snow will stay to the south, but that it would be a close call.

On Friday, I mentioned that the models had gone far to the south and completely removed the snow threat from our area, but that this was a known behavior. I pointed out that the models would come back north, and they have. I also maintained that a major snow event would be unlikely for most of the Finger Lakes, but that if snow did make it this far north, there would be a sharp cutoff in snow amounts.

It is my aim in forecasting to go beyond the models, use my experience and knowledge of the science of meteorology, and produce actual forecasts. I hope my consistency can help bring clarity to what is a complex forecast.

finger lakes weather forecast map showing four zones that have unique characteristics and expectations for snow Monday night and Tuesday morning, as explained further in the blog post text.
The Finger Lakes region will be on the northern edge of a winter storm Monday Night and Tuesday morning, leading to large variations snow amounts and high uncertainty in the fine details. Click to enlarge.

The Four Zones

For the northern Finger Lakes, shaded in green on the map that heads this blog post and is reposted here, there is little chance for any impactful snow. If the storm nudges towards the southern edge of its possibilities, some of these areas will probably not see even a flake of snow.

Shaded in light blue, the second zone stretches northeast from the western southern tier through the heart of the Finger Lakes and includes locations such as Dansville, Penn Yan, Geneva, Auburn, and Syracuse. These areas will likely be near the sharp cut off in snow, so amounts are highly uncertain and will likely be highly variable. Generally speaking, though, amounts are more likely to be on the low end with minor impacts.

In dark blue, areas such as Bath, Watkins Glen, Ithaca, and Cortland are likely to see accumulating snow, but just how much remains to be seen. The sharp cutoff may have less of an impact in these areas, but the core of the heaviest snow is also less likely to make it this far north. Moderate travel impacts are probably a good bet for Tuesday morning.

Finally, clipping the southeastern Finger Lakes in parts of Steuben, Chemung, and Tioga county, significant snow is likely in the purple shaded areas. If the core of heaviest snow makes it this far north, amounts could easily be near or over a foot. Even on a more southerly track, plowable snow is likely. Tuesday morning’s commute will be highly impacted.

Where to from here

I have detailed several times this winter my reasons for making a single snow amounts map for a given event. I have even drawn a snow map live on video with audience interaction. Due to the timing of this event, I will not be live streaming my snow map creation, but rest assured that I will once again be painstakingly drawing my map and tweaking it until I feel it is just right.

I expect to have the snow map ready for Monday morning’s typical blog post, which I usually publish between 7:30-8 AM. Since the map takes a long time to make, the blog post may be a bit delayed, but we will see.

Just writing this blog post and creating the two graphics shown has taken me nearly 2 hours this Sunday morning. This does not include the constant analysis and monitoring I have been doing for days already.

Again, my aim is to provide you with the best information possible by moving beyond what most modern weather forecasts and reports offer. If you find this approach helpful and worthwhile, there are several ways you can support my work.

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Follow Meteorologist Drew Montreuil:
Meteorologist Drew Montreuil has been forecasting the weather in the Finger Lakes region since 2006 and has degrees in meteorology from SUNY Oswego (B.S. with Honors) and Cornell (M.S.). Drew and his wife have four young boys. When not working or playing with the boys, he is probably out for a run through the countryside.

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