How to make sorbet have a snowy texture? I have a plastic ice-cream machine (two quarts). 

I water, sugar and lemon juice, cool it until it just starts freezing, and then put it into the ice-cream maker for an hour.

As a result, it comes out with ice clumps and if I put it in the freezer, it comes out hard.

One time, I made it actually come out with a "snowy" texture, and that can be placed in a freezer without hardening it. However, I don't remember what I did special then.

What should I do to get my sorbet snowy?
A variety of factors can change the texture of a sorbet:

The amount of sugar or other large quantity solutes (less dissolved solids, harder texture).

The rate of freezing (slower freezing, larger crystals).

The use of any "stabilizers" (guar/xanthan gum, gelatin, etc.). These interfere with the formation of large crystals. I believe the stabilizer I use is xanthan and guar gums, cold-soluble gelatin, and glucose but I can't remember the ratios I used.

I have started to use liquid nitrogen to freeze my ice cream and sorbet in my standard kitchen mixer. Once I did that I noticed that the texture was much finer, likely due to the stabilizer and the rapid freezing.

Related question: Creating a creamy sorbet