This is Snowflake #9 in the book of 100 Snowflakes. Instructions are on Page 48. It is pictured on Page 23 in Showcase.

“This snowflake takes its name from the Narbonnais, a sometimes-stormy winter wind in France.”

Finished diameter: 2-1/2 in. (64 mm)
Thread required: 7 yd (6.4 m)

All pattern samples in this book are made with size 10 thread and a size 5 (1.9 mm) crochet hook.