The Systemic Grammar Network notation is a non-formal knowledge representation language. We define a variant of the System Grammar Network notation and use this notation as a draft modelling language in the knowledge acquisition process of the VVEXP project. VVEXP is a prototype of a knowledge based system that predicts slipperiness on the roads. VVEXP has access to a real time database that contains recordings from more than five hundred field stations. One recording typically contains temperatures of air and road surface, wind speed and direction, dew point and precipitation. We use the METAMETH methodology, focus on the knowledge acquisition process and discuss our choice of draft modelling language. Other draft modelling languages that might be used in METAMETH are compared to Systemic Grammar Network. We conclude that Systemic Grammar Network was a good draft modelling language to represent the specific kind of domain knowledge characteristic of the VVEXP project.