Let me try to explain this in simple terms: You’re throwing a dart from about 30 feet away from the dart board. The bullseye seems like an impossibility. Yet, if your eyes are strong enough you just may be able to hit it. You are experienced, but this is a tough throw. Everything has to go right. Correct?
That’s the equivalent of what the storm on Saturday night has to do. It has to hit a window of opportunity so small that if ONE thing goes wrong you end up with nothing. The sample graphic is from the evening GFS. Notice the two streams of the jet stream-northern and southern streams. The southern stream must phase with that northern piece, but if it’s weak as currently modeled all we are going to get is a progressively weak wave of moisture that delivers the equivalent of a coating overnight Saturday into Sunday. This southern piece needs to be stronger, out of ahead of the northern piece, and then phase somewhere near Indiana or Ohio. Then it just might hit the bulls eye-us with 4-6 inches of snow.
Anyone good at darts? :}