I am re-posting this question as original post did not get any feedback.
On my MY02 WRX when starting in real cold weather (10 - 20 deg F) voltage gauge jumps to 16.7 V and holds at 16 V level even with headlights, defroster and fan on high for several minutes - until engine warms up. After that it gradually drops to "normal" : 13.8 V while driving and around 12 V while idling on a traffic light.
Did anybody had similar experience? I am not happy to see car electronics experiencing 16+ V even for couple minutes, but to demonstrate this to the dealer I would need a really cold weather and car spending night in dealership.