Winter to tighten its grip: Travel trouble overnight then weekend storm takes center stage

DAMP AND FOGGY

The haze hangs over the city Tuesday evening and that fog will thicken. Tiny water droplets will at times cling and create some slick surfaces. Freezing drizzle and flurries will linger through the night and be aware! It is very light but can cause problems if traveling late tonight and early Wednesday morning. Winter Weather Advisories are out for much of Illinois, and northern Indiana.

TRAVEL TROUBLE

More headaches could come by early Thursday morning as a weak low pressure races east toward central Indiana before daybreak Thursday. There is more moisture to work with late Wednesday night and it will stream into the state before sunrise and will impact the morning commute. At this time a period of wet snow is to develop on the storms northeastern periphery and reach central Indiana early Thursday. Warmer air will then ride southwest winds and may bring a brief change to freezing rain before becoming all rain by late morning. Slick travel is possible early Thursday with the potential of light snow accumulation and icy conditions before temperatures rise above freezing.

STORM BREWING

Still many days away but a new storm is a certainty for the upcoming weekend. The storm identified late last week of the European computer model has appeared on all long range computer models and looks to be far reaching. While there are more questions than answers, the storm is expected to bring an array of wintry weather along with a potential of severe storms as well.

This storm will be much different than last weekends and looks to be much more complex. Many factors are still coming together, one of which is the presence of the polar branch of the jet stream. This is a key component.

While the El Nino driven, southern branch of the jet stream carries the storm off the Pacific Ocean and across the Rockies laden with moisture, the polar jet is expected for the first time in over five weeks to dive south. At this time the marrying of these two jet streams (phasing) would lead to explosive low pressure development and rather large storm for much of the eastern half of the nation.

Winds blow strongest when sharp temperature spreads develop (gradient) and this weekend, with arctic air intersecting warm, gulf air the storm will be large.

The storm track is also a key and as of Tuesday night appears to be taking the southern route. I'm posting below the forecast surface map Saturday morning off two long-range computer forecasts. Low pressure location depicted here is prime-time for wintry weather in central Indiana. Note the web of pressure lines, much more wind will also occur with this weekend’s storm.

Then the Arctic blast! Bitter cold air will roar into the state behind this storm (that darn arctic jet stream) and send temperatures tumbling Sunday. We may dip below zero late Sunday and could fall to -5° by Monday morning.

At this time we know that many types of precipitation could fall across central Indiana but it is just too early to tell where. If you have plans this weekend, start thinking of alternatives but change nothing right now. Be sure to check back through the work week as we will know more as more date become available.

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