The call
What's going to happen, in one paragraph, no hedging.
A clipper drops southeast Saturday night and lays down 4 to 7 inches from the northern suburbs up through the lake counties, with the sharp cutoff sitting roughly along the interstate. South of that line gets a dusting and a lot of complaining.
The why
The setup, the models, and what they agree on.
The 500mb shortwave is sampled well by three consecutive runs and the ensemble spread on snowfall has collapsed to under two inches across the northern half. Frontogenesis maximises right where the deformation band sets up, and soundings keep the whole column below freezing, so this is fluff, not paste. Ratios near 15:1 do the rest.
What would change my mind
The specific things I'm watching that could flip this forecast.
If the shortwave trends 60 miles further southeast the heavy band shifts onto the metro and the northern totals come down two inches. I am also watching whether the low-level jet holds past 3am; if it decays early the band unwinds and the top end drops.