Any helicopter weather radar I have used (excluding that fitted to civilian AW machines) have been good down to half a mile for obstacle avoidance as long as it is in the correct mode. It's no good leaving it in wx mode because the gain is then fixed and non adjustable in order to optimise the observance of Level 3 weather returns which equate to an active thunderstorm (or very heavy rain).
In absolute contradiction of Double Bogey above, use of the correct Search mode is vital. There will be at least one which is optimisied for short range selection which will reduce the pulse length and increase the pulse frequency. When level at 200' or thereabouts, tilt control should be set about level which will give about +/- 3 to 5 degrees of scan above and below the horizontal depending on the diameter of the aerial. The larger the aerial, the narrower the beam will be in both horizontal and vertical plane. If the radar is set correctly, Black Rock should have been painting loud and clear.