Officials at Aintree have taken the decision to water the course overnight following a dry day in Liverpool.
The Grand National course is currently described as good to soft, good in places while the Mildmay course is good, good to soft in places.
Clerk of the course Sulekha Varma will apply five millimetres to the National course, with slightly less watering on the Mildmay track.
Varma said: “I am describing the Mildmay and Hurdles courses as good, good to soft in places, and the Grand National as good to soft, good in places ahead of Randox Grand National Day.
“We are watering both courses and will be putting 3mm on the Mildmay & Hurdle courses and 5mm on the Grand National course.
“By starting out wide, we are providing fresh ground every day, so the rails will be moved in three or four yards again so that on Saturday they are at their innermost position.”
The weather looks set fair for Saturday, with Varma adding: “Tomorrow is forecast to be very similar to today, which has been lovely. It’s going to be sunny, with just the slight chance of an isolated shower.”