By Kate Bilo

PHILADELPHIA (CBS) — Our latest winter storm is underway and this one is different from the others, in that it’s what we’re calling an “upside down” storm. Generally in our area, we see the highest snowfall accumulations in our north and west suburbs due to the higher elevations, but not this time. Today’s heaviest snows will fall from Philadelphia on south as a wave of low pressure rides along a stationary boundary.

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One impressive feature of this system is the sharp cutoff of the precipitation. In the north and west suburbs of Philadelphia, very little, if any, appreciable snow will fall. But to the south, heavy convective snows could total 10″. A widespread over the area where if you drive 40 miles south, you’ll see an entirely different landscape.

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We expect the snow to end in Philadelphia around 10am, then ending in South Jersey and Delaware by around 2pm. Cold air is moving in with the system as well. Temperatures will plummet through the afternoon, with maybe just a little rebound late if the sun comes out. Tonight, we plunge down to single digits again across the area, with wind chills once again in the subzero range. The record is 7 degrees from 1943 and it looks like we will certainly challenge that number.

This system was a fascinating one to watch in its development. It was a battle between a strong southern jet stream and an intense wave of low pressure moving in from the west coast versus a huge arctic high pumping cold air into the US. Generally speaking, I would tend to bet on the high most times, but in the days leading up to the storm, it looked as though it would push far enough north to bring snow to much of our area and much of the Northeast.

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On Friday, I mentioned a few models that were starting to show the high winning out and posting a more southerly solution to the storm. And it turns out those outlier models were on to something. Over the weekend, guidance trended south as the storm was not quite as strong as modeled, and the polar high eventually did win out, keeping the heaviest snows off to the south.