In order to answer the question it is important to know the makeup of the product you are using.

The N component of 28% (also known as Urea Ammonium Nitrate) is 50% Urea, 25% Ammonium, and 25% Nitrate. The urea, when applied to the soil, converts to the ammonium form which is stable in the soil. So, you have 75% of your N in a stable form which will not be lost until it is converted into nitrate. At soil temps below 50 degrees, this process is very slow. However, 25% of the N you are applying is in the nitrate form which is immediately subject to leaching regardless of the temperature of the soil, thus, you could potentially lose 1/4 of your N almost immediately. This I think would be unacceptable.