PJ2, for dual NDB approaches in Russia, an OCH (obstacle clearance height above the threshold or the airfield elevation) is defined, typically somewhere between 90 to 150 meters (≈ 290' to 490'), which for a typical Russian 2°40' glideslope corresponds to about 1900 to 3200 meters of horizontal visibility. Obviously, the reported wx was not quite adequate for these minimums.