Major winter storm strikes Minnesota Tuesday

March weather lion

March has been unusually quiet so far in Minnesota. That's about to change in a big way.

Our dry quiet start to March features a scant .02 inch of precipitation through this morning at Minneapolis-St. Paul International Airport. A string of days in the 40s and 50s produced widespread snow melt the past 10 days.

Now, the March weather lion is about to roar. The only remaining question appears to be exactly who will get the heaviest snowfall?

Winter storm watches and warnings are flying for much of central Minnesota for Tuesday.

• .3 inch snowfall at MSP Airport so far in March

• 5 days at or above 40 degrees since March 9

• 2 days at or above 50 degrees

• 16 inch snow melt at MSP so far this month

Storm brewing

There are still a few key details to be worked out regarding the precise storm track, but  one thing appears certain. Parts of Minnesota are going to get blasted with heavy wet snow Tuesday and Tuesday night.

A deepening low pressure system is tracking through Iowa into Wisconsin Tuesday.

Small track shift = big forecast changes?

There are still some key differences on the precise storm track and that could affect Twin Cities snowfall totals.

A more northerly track favors a mix and less snow in the metro. If the storm tracks further south/east, the Twin Cities gets clobbered.

In either scenario the heaviest snow axis in Minnesota sets up from Ortonville, through Morris, Alexandria, St. Cloud, Mille Lacs, Brainerd to Duluth and the North Shore. That's the zone most likely to get 6 to 12 inches or heavy wet snow with this system.

Here's another look at the developing system with precipitation type and track. Click the image below to see the forecast loop.

Once again, the Twin Cities is at the "temperature critical"edge (32 degree isotherm) of the heavy snow band to the northwest. If the Twin Cities manages to mix in some rain/sleet Tuesday during the daylight hours, that could reduce snowfall totals, especially just southeast of the metro.

If it's all snow, we'll get a pile. Why should this one be easy?

Here's the Twin Cities NWS first crack at snowfall totals with the system.

Historical snowfall tracks?

History can be a good guide for snowfall with storm tracks. Here's a look at the Cooperative Institute for Precipitation Systems analog, which lays out the heaviest snow band just northwest of the Twin Cities from Redwood Falls, Minn., to Duluth.

Here's the idea behind CIPS from the Twin Cities National Weather Service this morning.

Time to geek out on some weather data! Here is the average observed snowfall from the closest 15 historic matches to what is currently being forecast Tue-Wed. So, unless there is a major course deviation and if history can tell us anything, there is a good signal for 6"+ from west central MN to northeast MN and northwest WI. The Twin Cities and Eau Claire would be outside of the heavy snow band, but St. Cloud would be very close

Duluth looks to be near the epicenter for this one. Here's the early view on snowfall totals from the Duluth NWS.

Tight 'snowfall gradient' near metro = big boom or bust potential

The eventual storm track, and temp profile in the lowest mile of the atmosphere means the Twin Cities is right on the edge of the heavy snow zone once again.

A slight track shift east or south means the heavy snow zone shifts toward the metro and we get clobbered with heavy snow. A more northerly track and milder (above freezing) air mixing in Tuesday during the daylight hours changes precip to a rainy/wintry mix, and we get much less snow.

Either scenario is still possible at this point, or something in between.

Here's the overnight snowfall output from the National Oceanic and Atmospheric Administration's Global Forecast System, which places the Twin Cities on the edge of the heavy snow zone, and brings a pile of deep snow with some 16 inch snow totals possible toward Duluth.

Bottom line: I want to see what trends today's forecast models show regarding track specifics before I sign off on potential metro snowfall totals.

Stay tuned as we track the latest model runs this morning, and again tonight to tweak track and snowfall totals with this storm.