unexpectedly strong snowstorm; sudden snowstorm
Refers to a sudden, intense snowfall that catches people off guard, often causing traffic disruptions. The term likens the unpredictable nature of such snowstorms to guerrilla warfare.
See also: ゲリラ
The expressway was temporarily closed due to a sudden snowstorm.
The forecast said it would be sunny, but a sudden snowstorm started in the afternoon.
Compound of ゲリラ (guerrilla) and 雪 (snow), modeled after ゲリラ豪雨 (guerrilla rainstorm). The 'guerrilla' element emphasizes the sudden, unpredictable nature of the snowfall.