Kate, who is more than eight months pregnant, will stay at home, but William and Harry are expected to be among the congregation to watch Thomas van Straubenzee marry Lady Melissa Percy.
The Duchess' final official public appearance was last weekend when she attended the Trooping the Colour ceremony with other members of the Royal Family.
More top news
Over the next 24 hours we are going to see snow and ice across many parts, although it is looking calmer from Sunday onwards.
A young grey seal found in a farmer's field on Monday is making progress say RSPCA staff. He's thought to have a head injury.
The UK economy, boosted by the inclusion of the sex and drugs industry in the calculations, is now the world's fifth largest, but only just.