Wisconsin Weather

Heavy Snow Possible in Early Week Storm

By Justin Poublon
January 20, 2019 - 4:30 PM CST | 383   0

A positive tilt low pressure system will bring widespread accumulating snow to Wisconsin starting Monday night and lasting until early Wednesday morning. The storm will go down in two main phases:

  • Phase 1: Northern Wisconsin - Monday night into Tuesday morning in northern Wisconsin

  • Phase 2: Central and Southern Wisconsin - developing during the day Tuesday, peaking Tuesday night centered on central/southern Wisconsin but still light snow in the north.

Below is a break down of what to expect by region and phase:

Phase 1: Northern Wisconsin - Monday night into Tuesday morning

Will begin as early as 6 PM Monday night in far northwest Wisconsin, spreading across northern Wisconsin overnight. This looks like a long duration light snow generally south and east of Duluth/Ashland with heavier amounts north of that. 6"+ is expected across northeast Minnesota and portions of upper Michigan.

PHASE 1 - Monday night into Tuesday. Snow moving into northern Wisconsin. Nothing happening in the southeast.
PHASE 1 - Monday night into Tuesday. Snow moving into northern Wisconsin. Nothing happening in the southeast.

Phase 2: Central and Southern Wisconsin - Tuesday into early Wednesday AM

The key point is start time: around mid-day Tuesday. So don't worry if nothing has happened yet when you wake up on Tuesday. It's coming.

Several inches of snow are possible. Question is exactly how much? Just 3-6" or will there be more? At the time of writing there was a lack of consistency in the models. There is a chance a 6-9" will be needed across southern Wisconsin (read discussion below for details). I hope Monday morning model runs are more concrete on this so I can interpret them and get the latest forecast out to you!

Chance of rain or an icy glaze developing along the WI/IL border.

Tuesday into early Wednesday AM - Possibility of heavy snow in southern Wisconsin.  Watching north-central Wisconsin too. Rain mixing in across the far south.
Tuesday into early Wednesday AM - Possibility of heavy snow in southern Wisconsin. Watching north-central Wisconsin too. Rain mixing in across the far south.

Storm Total Snowfall Forecast

★ Expect changes to the forecast on Monday as model consistency improves and we can add more detail to the forecast! If you live in Madison or southern Wisconsin: assume 3-6" but don't be surprised if future forecasts come in higher.

Snowfall forecast for Monday night through early Wednesday AM. Uncertainty on southern Wisconsin. Need more consistency.
Snowfall forecast for Monday night through early Wednesday AM. Uncertainty on southern Wisconsin. Need more consistency.

The next forecast is planned for Monday morning. I'm looking at every run of every model to make sure you have the best information! Please check back later!

FORECAST DISCUSSION - *IMPORTANT*

If you know how I operate this should be an interesting moment. Despite enough consistency in the major medium range models ( 12GFS,12GFS3, 12EC, and 12Canadian) to add higher snow accumulations to the snowfall forecast...the best thing to do right now is wait for more information and consistency. My gut feeling is to push and that I will likely need a 6-9" zone across southern Wisconsin. This is supported by the latest 18zGFS...but there is definitely a reasonable doubt on whether that will even be needed. I think a little patience and apprehension is good in this situation.

Why I am cautious? Specifically because of the latest high resolution 18z NAM model run which does not support heavy snow in southern Wisconsin. It did on the 12z run. Yes it is the 18z. It could just be a bad run. The system is coming ashore as we speak. With a positive tilt partially out of sync low pressure system it should be expected.

The NAM has been the hot hand lately. Since the 12z run, the NAM went from 12" to maybe 2" in the same location on subsequent runs. We usually don't have major swings within model late in the forecast cycle but this does occur on occasion. Again, my gut says push. I wouldn't be surprised to see it swing back on the 00z runs. I would go strictly by the GFS and EC but EC did not perform well on Friday. Interestingly the EC is doing some flip-flopping too. It shows high snow totals but not in the same place as the GFS. Which one is right?

In conclusion; there is absolutely no harm in waiting here because we are still 50 hours away from arrival in southern Wisconsin. There is reasonable doubt. There is time. Tomorrow once we are a couple model runs closer to the event; I hope to have more clarity on heaviest amounts.

Historical Comparisons

The GFS shows a very similar but stronger version of a heavy snow event three years ago on Jan 25, 2016 which brought 6-8" in a band across southern Wisconsin. If we were forecasting simply based on magnitudes: reaching 10"+ amounts would be no problem Tuesday night in southern Wisconsin. Not every storm is the same and I can't forecast simply based on that.

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