If you get some nice days then it can be productive. We often get warm fronts that move in and give us 2-4 nice days ina row. Usually by the second dayt eh fish are responding well to nymphs and dries in the afternoon. Then by the third day they will often be looking up regularly. I tyically use a dry/dropper rig with a Royal Wulff or EHC on the surface and a bead head green or pink weenie down low. Also running nymphs through deep pools will often bring up a nice fish or two. If the weather is real cold I don't even bother, the fish develop lockjaw then--Larry
