Growing odds for significant snow event Friday
Keep that snowblower tuned up. The odds are growing you'll need it again by Friday night.
The system
A developing low pressure storm tracks toward Chicago Saturday. The system looks almost certain to spread a large snow shield north into southern half of Minnesota Friday and Friday night into Saturday.
All snow for Minnesota
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It's cold enough for all snow with this system, so no rain-snow line issues to deal with here. The only question appears to be where the heaviest snow bands will lay out across southern Minnesota, and if they will include the Twin Cities metro.
We're moving into the 48 hour forecast model target-zone sweet spot to begin laying out snowfall coverage and potential totals. Because this system has plenty of cold air to work with, it should be an efficient snow-maker. The size of the snow shield looks impressive, covering most or all of southern Minnesota by late Friday.
'Stellar dendrite' growth zone close to MSP?
One thing we look for as meteorologists to pinpoint heavy snowfall bands is where the Dendritic Growth Zone (DGZ) will set up. This layer in the atmosphere has just the right temperatures and saturation to produce big 'stellar dendrites' that can pile up quickly to enhance snowfall totals.
Optimal conditions for the production of stellar dendrites include a temperature around 10,000 feet above ground between -12C and -18C. Current forecast models like NOAA's GFS suggest the DGZ could set up right over the Twin Cities by Friday evening.
6" to 12" totals for southern Minnesota?
Again, it's still early to put too much faith in model snowfall projections more than 48 hours out. But NOAA's GFS model did an excellent job leading up to last weekend's snow event. Here's the GFS snowfall output for Friday and Saturday. I wouldn't focus so much on specific inches here this early, but more on snowfall coverage and where the heaviest snow bands are likely to set up.
Travel from the Twin Cities south looks bad once again. Decorah, Madison and Chicago's northern 'burbs could get a major pile of snow if this solution verifies.
Stay tuned.
Arctic Sunday
Arctic air invades Minnesota behind the system Saturday night and Sunday. Wind chills plunge below -30 this weekend.
The Arctic plunge is brief, maybe 36 hours of sub-zero pain for the Twin Cities from Sunday morning through Monday afternoon. Temperatures moderate into the 20s and possibly toward 30 next week.