I Am Considered Pre-diabetic With My First A1c Test 6.4

I am considered pre-diabetic with my first A1c test 6.4 and second 6.1. I lost 30 lbs in 4 mo after the diagnosis and I have regularly worked out with a trainer 10 yrs. I have been monitoring my glucose for 6 months and my numbers have been steady for fasting, in the 90-110 range, and never higher but usually low in the 130-140 range 2 hours after a meal.
Last night my before bed test showed 296! So I test a few minutes later and showed 278. For dinner I had eaten 1 stuffed pepper in tomato sauce with 2 thin slices of baguette and 2 glasses of white wine. ( this would be a meal of approx 500 calories and would be an average meal for me).
This morning my fasting level was 146, the highest it's ever been.
What could account for such a considerable change in one day?