I think you may be looking at it in a wrong way. The forward voltage drop is specified with a average current. This voltage drop can vary with temperature. In fact the older version of the 1N4148 the 1N914 has been used as a temperature sensor on occasion by monitoring the forward voltage with a specified current flowing thru it. I also remember seeing a circuit or two that used the forward voltage of this type of diode as a voltage reference source.