Did the Nazis know about the bombing of Dresden in advance?

As we discussed here a few months ago, in recent years, German requests that the allies apologize for bombing German cities during WWII have been getting louder.
Now the Scotsman raises the intreaguing possibility that Germany actually knew about the bombing of Dresden, exactly 60 years ago, in advance -- and rather than moving its residents out of the city at night time, as it had done elsewhere, left them to die:

Military investigators are checking a letter written by a German anti-aircraft gunner to his parents in the city, which gave the date of the raid two weeks before the fateful bombing in which 35,000 civilians lost their lives.
The letter has opened a debate in Germany as to whether the Nazi leadership, including Luftwaffe commander Hermann Goring, might have decided to leave the city to its fate for propaganda reasons, or even as part of Hitler’s belief that the German people, having "failed" him, deserved to be left to their fate.
The gunner, Günther Brückner, was stationed at an airfield used by special German Air Force intelligence planes that snooped on Allied radio traffic. His now yellowing letter has added to the controversy over the raid, which has been described by some critics of the Allied bombing campaign as a "war crime".

Investigations seeking to prove that the letter was indeed written before the raid are currently being conducted.