With heavy wet snow plus a warm engine and radiator, you may have kicked some water into the dist cap. I have had this happen in our "warmer" winter weather. The water may follow the sides of the coil past a bad spot in the upper dist cap gasket, and "poof" the tractor engine kills. The same thing will happen if the antifreeze overflows a bit. So pull the dist cap off and check for any moisture inside.
And the other guys are right about checking the starter, as it is probably still engaged into the flywheel ring gear. I doubt that your EI has been fried if it was working reliably before. Don't put too much force on the starter if it is still engaged, you can break out the sleeve bearing in the starter's end plate on the bendix side. The end plate is aluminum and I have seen a number of them broken. Loosen the starter bolts and wiggle it real good while rocking the tractor in gear.
Paul in MN