April is the most unpredictable month of the year and driving conditions can vary from spring like conditions in the lowlands to full blown blizzards and convoy driving in the mountains. Some of the more scenic roads like Aurlandsfjellet, Sognefjellet and Trollstigen will still be closed, leaving you with the less interesting main roads.
Early or late April would also make a difference.
Norwegian roads are rarely closed because of weather, mostly at mid Winter. Key point is that Geiranger road (# 63) is always closed until mid May because of snow remaining and avalanche hazard. What you can not plan is bad weather for instance on road 15. Early April is still Winter in the interior and on the mt passes, if you dont have any Winter driving experience this can be demanding.
You can be Lucky and have a day like this
Or like this
In the interior temperatures can drop to -10 C even in April