How can I refer to the Winter Bash event in a shorter and more descriptive way?

brumal: 'indicative of or occurring in the winter' (Merriam-Webster)

No subject has more engaged the naturalist in all ages than the brumal retreat of the swallow. (source)

The wind was whipping the snow into a flurry fury, bruiting the eddies about like brumal rumors. (Joan Connor, 'The Folly of Being Comforted'. TriQuarterly, Fall, Iss. 123; pg. 169, 2005)

Examples from the OED (which defines it as 'ff, belonging to, or characteristic of winter; wintry'):

1813  Belfast Monthly Mag. 31 Jan. 47/1        
Dark indeed are the brumal days that have no sun shine.

1870  J. R. Lowell My Study Windows 32        
What cheerfulness there was in brumal verse was that of Horace's.

1934  E. Linklater Magnus Merriman vii. 84        
That brumal solitude derived from knowledge of hunger in December and thrashing gales in March.

1983  M. O'Donoghue Jedder's Land (1984) 41        
Clumps of snowdrops..had magically withstood the brumal cold of the past week.

2001  P. Ball Bright Earth viii. 205        
Here is a very different kind of atmospheric lighting: cold and brumal, veiled in the shadows of a low sun.