A lot depends, as has been stated, on the type of aircraft. I assume you are referring to a B-747/777 or A380 type aircraft. First, if the plane is stopped at the gate, empty, and dark, the plane might get blown around a bit, maybe even flipped, but the main threat would be flying debris. You are not going to have a hull loss because the plane was blown around a few feet. Most likely, there would be slight debris damage to the body of the aircraft, but because you are referencing an EF-1, there will not have been a lot of damage to surrounding structures, and most likely not that much damage to the aircraft either.
Now, say for example that the plane is on final, or has just landed or taken off, you are dealing with a whole other scenario. First, though, as a word of explaination, the FAA would have put a ground stop on the airport long before severe weather capable of producing a tornado was anywhere near the field as numerous planed have been downed due to winds on takeoff or landing, so this scenario is highly unlikely. However, if this did occur, you could (probably would) be looking at a great loss of life. The period of time just before and after takeoff and landing is the most delicate in terms of aircraft stability. Pilots are highly trained to respond to strong gusts of wind at this point, but a tornado could most likely flip a plane, or cause an unrecoverable deviation from its flight path, either due to being slammed into the ground, being pushed over, or the pilot overcompensating for the sudden lift.
Hope this helps. Would like to see this discussion continue.