The definition of Slush according to Webster's Dictionary :partially melted snow or ice
Urban slang dictionary definition of slush : a promiscuous female, who is easy to bed.A woman who is a mixture of a slut and a lush
A Winter Fly Fisherman's definition: a daily pain in the ass
The trick with slush is forecasting the end of the daily hatch. The slush hatch is very thick early in the day, sometimes dense enough to give your flies a boat ride instead of a scuba. The last thing you want to be doing in this situation is waiting stream-side while the fish are keyed in on Midge slurpees.
The basic formula for leaving the comfort of the igloo goes like this;You are looking for lows in the teens. Anything colder, especially for an extended period of time may leave you at the vise. High teens as a low usually means the slush will be gone between 11-12 in the morning as long as the high temps reach 30 or better. Sounds simple but it can trip a dude on a non adjustable summer schedule. We are constantly explaining why we DON"T want to pick you up at 6 am during the winter. Sleep in people, enjoy your vacation, the river is not ready for you, it's slushy out there.
Waiting for the slush to burn off after dragging the boat through the snow to the point of no return can be painful
I don't have one of those World Class Tailwaters in my back yard, Mother Nature runs the flow show around here. There is a daily ebb and flow almost like a high tide and a low tide which in turn effects water temperature and slush. In the summer months it's not uncommon to see a 8-10 degree fluctuation in the water temps and when daytime air temps get warmer you want to be fishing water temps as they fall. Winter water temps and flows bounce around too, just not as much. A water temperature change of 3 degrees is about all you get during winter but it makes a difference. During the winter a smart angler is there when the water is the warmest.
Don't let warm air temps fool you into thinking the water is warming up also. When some tease of a weather pattern slides in and tricks everyone into thinking spring has sprung, the water temps are actually dropping. Warming water rises and bangs against the bank ice cooling the water temps instead of raising them. If you start to change your tactics assuming the fish are as comfortable as you are before the water is ready, you may be in for a long day.
Embrace the pace of winter fishing.