The Eric Factor: The winter systems that give us the biggest impact

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This morning, I thought we would get a jump on the winter season. Last year before Thanksgiving we got our first big snowstorm with 9.9 inches of snow in the Quad Cities.

Here's a little refresher course on winter storm tracks. Depending on the track of low pressure (yellow arrows), we get much different weather.

The Rainy TrackrainytrackWhen low pressure passes to the west of the Quad Cities, there is a southerly wind for the majority of the storm system. This keeps us in a warmer, more humid airmass. Rain can be excessive, especially if it's falling on top of frozen ground and snow. Flash flooding has been known to occur in storm tracks like this.

The Rain/Snow Mix Trackrainsnowtrack

When low pressure passes directly over us, it usually brings us a mix of rain and snow. The most tricky storms to forecast are those that pass from St. Louis to Milwaukee, or slightly east of the Quad Cities. This makes it difficult to forecast how much snow will fall as low pressure moves north. Meteorologists must calculate the amount of rain that will fall before the column of air above gets cold enough to produce dendrites (snowflakes). If the timing isn't perfect, the snowfall forecast will be less than reliable. Again, these are the trickiest!

The Ice Storm TrackicetrackIt's been many years since Eastern Illinois and Western Illinois has seen an all-out full-fledged ice storm. This is the storm track that yields the biggest impact. If strong low pressure moves out of Kansas and Oklahoma, tracking toward Detroit, Michigan, it's able to bring lots of moisture up from the Gulf of Mexico. So long as the track of low pressure (yellow arrows) goes to our south, we're in the cold sector of the storm. As moisture is lifted up and over the system, heavy rain can fall onto a sub-freezing surface...creating ice accumulation.

Ice storms can be crippling. The worst can cause some cities and towns to lose power for days.

The Snow Storm TracksnowytrackHere it is! A snow-lover's dream usually comes with a weather map that shows developing low pressure coming out of Texas or Oklahoma. As low pressure rapidly intensifies, it turns left. If that happens over Memphis with a track up into Michigan, we can get literally dumped on! December 1, 2006 is one such storm that took this track. I was working as a Meteorologist in Rockford at the time, forecasting 8-14 inches of snow to fall overnight on November 30th. The snow began after midnight, ending around 9am with 10.7 inches of snow falling on the city. It was the biggest single-calendar-day storm the city had ever seen. And it was the biggest of that winter season. And in perfect winter storm tracks, the cities of Rockford and the Quad Cities usually receive very similar snowfall amounts.

Are you hoping for big snows this Winter season? Chime in on my Facebook page. I'd like to meet the other snow-lovers out there!

-Meteorologist Eric Sorensen

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