I don't think the excess sand is an issue that has had much research done on it so I don't think my opinion is worth much, but I don't happen to think it has anything to do with what's happening now, specifically the current weather or snow cover. I think the factors that affect this years sap happened last fall. Rainfall, sunlight, and even if there was a late season thunderstorm that passed over your bush and dumped a lot of nitrogen from the lightening.