How did 30+" of snow fall? (1-30-12)
The mega lake effect event from 1/30/2012 produced an impressive snowfall over parts of Oswego county. The highest official snow total reported was 32.5” in the city of Fulton. Following is a map of all the reports we received either through Facebook, called, or e-mailed into the office.Admittedly, I was a bit removed from all the nuances of the forecast, since I wasn’t in the office sweating out the specifics. I spent some time focusing in on the movement of the heavier band of snow, which arrived between 10 pm and midnight, but I didn’t spend a lot on the lake effect snow forecast. After a quick glance through some of the maps this evening, there really was no indication of such an impressive event.The heaviest snowfall occurred Monday morning, when snowfall rates of 2-3”/hour were recorded near Fulton. A quick glance at the upper level maps, showed temperatures at around 5000 feet above the lake in the low minus teens Celcius. Yeah, that’s cold, but our bigger events tend to have temperatures at this level around -20C.Here is the map for 850 mb (5000 feet)That is the saddest looking 850mb map I’ve seen for a big lake effect snow event. You would like to see a nice “u” shaped trough over the Great Lakes. There actually is a ridge (upside down “u”) building into the Great Lakes. About the only thing I see here is the possible directional convergence of the wind. The 850mb wind in Albany is from the NW and in BUF, the wind is from the west. Without that cyclonic wind flow, moisture input from the upper Great Lakes was minimized to perhaps even non-existent. From what I’ve been able to surmise from radar data, Lake Ontario did this all on its own. If there was contribution from the upper Great Lakes, it was minimal. Our mega lake effect snow events tend to produce thunder and lightning. We did have some Sunday night, as expected, with the passage of the strong upper level jet stream energy. But as of this writing, I have not seen any reports of thunder with the snow band this morning.So, why was this event such a prolific snow maker, if only for a few hours? Without more detailed information and research into this specific event, we won’t have a definitive answer. If you had to pin me down tonight, my educated guess would be the heavy snowfall could be attributed to the very cold air up around 18,000 feet. This morning, 500mb temperatures look to be around -30C over Lake Ontario. That type of cold is usually related to bigger wintertime precipitation events for us.This is the weather map at 500 mb (18,000 feet). The red dashed lines are isotherms in 2 degreeC increments, and it looks like the -30C line is over Lake Ontario. Additionally, as Jim Teske showed on the 5 pm news tonight, Lake Ontario is running about 2C above normal in temperature. That’s just that much more heat and energy available to produce snow. So, overall, the bulk of central New York really wasn’t all that far off from our forecast. The exception of course was that narrow corridor through Oswego county, which saw close to 3 feet of snow. That area sticks out like a sore thumb. Obviously something very small scale set up a band of intense lake effect snow for several hours over one spot. I can honestly say that looking over the maps, there is no way a snowfall forecast of this magnitude would have been made...by anyone. The processes that go into making lake effect snow are running right along the envelope of our understanding of how the atmosphere works. That’s the challenge of lake effect snow. It is a very small scale feature that develops sometimes out of nowhere. It’s not like a nor-easter moving up the coast that is there and we can watch head our way.Needless to say this is all a learning event for us. I’ve been doing this 20 years, and no matter how much new we learn, there is always something unexpected that happens. It is our job to limit as much of the unexpectedness. Hopefully, these write ups give you a bit more of a glimpse into what we do here in the office. There are no dart boards. No secret tell all weather map. We roll up our sleeves everyday and come up with the best forecast we can. When things go wrong, we try to figure out why, so we don’t get caught again.
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