Heaviest snow zone in flux; 12+ inches possible in southern MN

It’s game on for heavy snow in southern Minnesota Friday.

But there are still a few critical forecast questions to play out as the storm approaches Minnesota Friday morning. Here is my latest thinking on the most likely storm evolution and impacts.

Storm headlines

• Winter storm warnings are posted from the Twin Cities south into Iowa and east into Wisconsin.

• The precise storm track is still in flux on forecast models. This may impact the ultimate location of the heaviest snowfall bands. But a major winter storm will impact most of southern Minnesota from the Twin Cities south and east Friday.

• Expect the heaviest snowfall and worst travel impacts Friday afternoon through Friday night.

The storm

A well developed low-pressure system will track from Kansas into southern Wisconsin Friday. That track is favorable for heavy snow for southern Minnesota.

The system has plenty of moisture to work with. NOAA’s GFS model (and most others) develop snow in southwest Minnesota along Interstate 90 by 6 a.m. Friday morning. The snow zone likely arrives in the Twin Cities from southwest to northeast between about 9 a.m. and noon Friday.

The heaviest snow bands still appear most likely (just) south of the Twin Cities across south-central and southeast Minnesota.

Snowfall totals

• There is high certainty this storm will produce a band of 6 inches to 12-plus inches along the heavy snow axis.

• There is still uncertainty about precisely where that heaviest snowfall band will set up shop.

The middle ground of forecast solutions right now favor the heaviest (1 to 2 inches per hour) snowfall bands Friday afternoon and evening setting up from near the southern Twin Cities southward along and either aside of a Mankato, Northfield, Red Wing, Minn., to Eau Claire, Wis., zone. This could include part of the southern Twin Cities.

It should be noted that NOAA’s NAM forecast model products push the heaviest snowfall zone northward right into the central Twin Cities. This solution would suggest a foot of snow in the Twin Cities.

The old-school forecasters used to say the NAM was often “too far north” and too slow. That may still be a factor favoring keeping the heaviest snows just south of the inner Twin Cities core. So we’ll be watching other models for agreement. NOAA’s 18Z GFS also suggests double-digit snowfall is possible in the heart of the Twin Cities.

Here is the latest available snowfall map as of post time from the Twin Cities National Weather Service.

So here are the key storm points as we approach Friday.

• Winter storm warnings are posted from the Twin Cities south into Iowa and east into Wisconsin.

• The precise storm track is still in flux on forecast models. This may impact the ultimate location of the heaviest snowfall bands. But a major winter storm will impact most of southern Minnesota from the Twin Cities south and east Friday.

• Expect the heaviest snowfall and worst travel impacts Friday afternoon through Friday night.

• Winds will gust to 30 mph late Friday and Friday night causing blowing snow.

Current thinking on snowfall totals by Saturday morning

• St. Cloud through Pine City and far north Twin Cities: 1 to 3 inches

• Most of the Twin Cities 4 to 10 inches (heaviest south)

• Southern Twin Cities through most of southern and southeast Minnesota 6 to 12 inches (locally 12-plus inches)

We’ll get one more major forecast model runs late tonight before the snow flies tomorrow. Keep an eye out at @MPRweather on Twitter for updates later Thursday night. And we’ll have Updraft updates early Friday morning and throughout the day.

Stay tuned!