Rain in PANC at -20c yesterday

Hi,I did a forum search on this here and all that turned up was one guy that fixed it with B644 update from Feb of 2011. This purch of ASE was made a month ago so I think I am up to date here with Build 647. So Yesterday morning I am sitting on the ramp at Anchorage PANC in the predawn hours for hours trying to figure out how to get this new MD11 fired up properly and it starts raining at -20c!. The sky was also few clouds only, some mid level stratus. The metar I got on ADDS an hour earlier was clear and the TAF was all clear untill 12 hours later when it was to start light snow. I did not check the metar in ASE for I was in full screen mode and did not want to take a chance on crashing the sim, mine crashes sometimes when switching to many times. The ATIS report I got from Radar Contact was -20c on the temp as well. It only rained for 10 minutes then it stopped and never happened again.What may have caused this?