The snow storm that hit Chicago Friday into Saturday November 20-21 was an important insight into winter even though it was not out event. I started tracking it as an example of the storm pattern in an active year. It is only the first event, but demonstrated a very important contrast that might surprise many people and I thought this snow photo with the stop sign was symbolic to add pause and examine this further. Needless to day, this was the second highest snowfall on record for the month and the third snowiest single November day for the Windy City. Compare the snow total to the forecast map below showing how this overachieved. However, it has also been one of the warmest Novembers as well.
This was not El Nino, but rather the warm pattern of the Pacific Decadal Oscillation that was responsible for shooting a fast moving storm across the northern US. Yes, big snowstorms can fall in an overall warm pattern. But the storm track is what I was interested in. Storms this year will race east like a slingshot due to faster upper level winds. The net result is that storms will push farther east, and in this case, delayed the turn north, keeping Chicago in the colder and heavier snow zone.
Now compare the latest map of snow totals, much higher than the forecast for the city. I discussed this in my post before the storm hit. The event verified on the high end of expectations near 1 foot, even with the warming from Lake Michigan. The local NWS office had the city with less than six inches.
This graphic from NWS Chicago explains it all.
Now we get the cold air following this pattern. This is something that plays right in to my winter outlook. But for the short term, I will have more on our forecast through Thanksgiving in my next update.
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