(WSYR-TV, Syracuse) Humble pie? Perhaps a small slice. Many of us awoke this morning expecting school delays/closings. I snowblowed 9" of lake effect snow from my driveway this morning in Cicero. For many, last night's snowfall only resulted in a few inches of snow. This my friends, is a perfect example of why there's more than cold air and a warm lake involved with lake effect snow forecasting. I though I'd just run through my thought process a bit when I put together the forecast Monday afternoon.
Cold air? You betcha. Temperatures at 5000 feet over Lake Ontario this morning were around -20C. The lake water temperature is running around 5 or 6C. That's a difference of 25 degrees. That's huge! All we need is a 13 degree C difference.
The cold wasn't the problem. It was the ambient atmospheric moisture and the structure of the jet stream over us. The jet stream pattern over us was one that produced rapid changes in wind direction. Winds in the lower atmosphere were WSW through the day Monday. Then with the passage of a wave of energy in the jet stream (and an arctic cold front at the surface) The wind quickly shifted into the northwest. For a brief time, say from 5 pm to 9 pm Monday evening, things set up perfectly for a contribution of moisture from Georgian Bay. I showed the connection during the evening newscast. In that 4 hour period, everything was maximized, and we were able to get 1 to 2 inches per hour in a very narrow band from Wayne County, through northern Cayuga, extreme northern Onondaga, Madison and Oneida counties. Doing the math, that's a good 4 to 6 inches in that time frame. This shows the volatility of the situation.
Then, we lost the Georgian Bay connection. The changes occurring at the jet stream level were coming too quickly, and our winds in the lower atmosphere turned a bit more northerly. Now, we had dry arctic air feeding south over Lake Ontario. Sometimes with a west wind carrying the cold air over the whole length of Lake Ontario we can moisten up the atmosphere. Coming from a northerly direction, the cold and dry air was crossing the narrow axis of Lake Ontario, and the resulting snowfall was much lighter.
So we were left with what we woke up to this morning. The thing that gnaws at me as I saw all of this unfolding, just as I described above. Probably 2-6" would have been a better forecast, than the 4-8" I went with for a forecast. I guess I was a bit chicken about going lower than what I did, given just how big the temperature differences were between the air and lake water. I violated a golden rule that I have and that is the feeding in of upstream moisture into the lake environment. Of course, hindsight is always 20/20, and when you're in the heat of battle, sometimes your vision gets somewhat clouded over.
Last night was a learning experience for sure. While figuring out challenging forecasts and being on camera can be difficult, because you always have to own up to what you say on camera, I find things like this fueling my passion to figure out the weather, and try to get better next time.
I welcome any comments or questions. We're discussing on the Storm Team Facebook
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