As a long-time skier in the French Alps, I always found Meteo France forecasting to be surprisingly accurate, especially given the unpredictability of weather in mountain areas.
The UK Meteorological Office though......more interested in preaching the global warming climate change mantras, even though they can't forecast tomorrow's weather worth a damn.
Maybe they are great in France, but since the BBC switched to them, the BBC's forecasts have been pretty bad. I still find the met office more reliable.
That said, I always prefer the local weather organisation as they know the climatic nuances. Also note for Sochi it is a very long city, so forecasts for the centre could be quite different from the Autodrom area.