Winter storm warnings in central Minn.; Twin Cities rides snowy edge

Razor's edge

This forecast should come with a warning label.

Ideally, meteorologists like storm systems that inspire "high confidence." We want agreement on a consistent storm track and temperature profile within an inbound storm. We look for a reasonably consistent output on the total amount of available moisture. We want the major urban areas like the Twin Cities to be right in the middle of the heavy snow zone -- or the no snow zone -- not on the edge.

Keep dreaming weatherman.

There are still a few critical things we don't know about Tuesday's incoming winter storm. Here's the latest breakdown about a system that looks to dump heavy wet snow in much of central Minnesota, with the Twin Cities riding the mercurial edge between the heavy zone and the no snow zone.

• Winter storm warnings in effect Tuesday for a big swath of western, central and northeast Minnesota.

• Winter weather advisory in effect including the Twin Cities metro area Tuesday.

Latest storm track and timing

The suite of several forecast models I favor in the Weather Lab are coming into closer agreement but still have critical differences on precise track temperature profile with this system.

The consensus track takes the system into southern Iowa, then re-curves into southern Wisconsin. That's a favorable storm track for heavy snow in central Minnesota.

Here's another look at the most likely storm track adding in precipitation timing from the National Oceanic and Atmospheric Administration's National Digital Forecast Database.

Here's a good look at how the Twin Cities office of the National Weather Service projects precipitation timing and totals as the system evolves.

A couple of key points with the system.

• A rain snow mix transitions to all snow for west central through north central Minnesota overnight into Tuesday morning. Expect snowy and difficult travel Tuesday in and near a zone around Granite Falls, Madison, Alexandria, St, Cloud, Brainerd, Mille Lacs and Duluth.

• The heaviest snow band should hover north and west of the metro most of the day Tuesday. That should mean a relatively snow-free morning rush and midday. A rain snow mix should move  into the metro toward afternoon rush Tuesday

• The Twin Cities should see a transition to all snow Tuesday evening, with the heaviest snow potential overnight. The northwest metro could see some 6"+ snowfall totals.

• The heaviest snow zone of 6 to 12 inches or more likely will run from near Granite Falls and Alex through St. Cloud and Mille Lacs through Duluth and along the north and south shores of Lake Superior.

Here's the projected totals from the Duluth NWS.

Metro: boom or bust potential still there 

To call this a "low confidence" forecast for the metro is accurate. At this point we're still 24 hours our from most of the accumulating snowfall for the metro.

I want to see what tonight's and Tuesday morning's final model runs before the snow flies for real. At this point, I am keeping the heaviest snowfall totals northwest of the metro -- thinking generally in the 2 to 6+ inch metro range from south to north. Any small track changes can drastically change snowfall totals.

Hers' a look at NOAA's Global Forecast System and  North American Mesoscale Forecast System snowfall output for the Twin Cities as of late Monday.

The GFS snowfall output hints at the notion of a wide snowfall gradient across the Twin Cities by Wednesday morning.

Stay tuned. This storm is still evolving!