It may be weak, but we can still measure it quite accurately:
“...Concluding on a lighter topic, let me remind the GGP community of what I recall as probably the most memorable moment of the first campaign. It occurred at the GGP Workshop in Munsbach Castle, 1999, when Virtanen was describing the effect of snow cover on the residual gravity at Metsahovi. He showed a figure of gravity increasing by about 2 microgal over a 4-h period as men shoveled snow from the roof of the SG station, when a member of the audience asked why there was an interruption in the rise of gravity, Heikki said this was a 'tea break'...”
D. Crossley, in Journal of Geodynamics 38/3-4 (2004), p. 234.
“...Concluding on a lighter topic, let me remind the GGP community of what I recall as probably the most memorable moment of the first campaign. It occurred at the GGP Workshop in Munsbach Castle, 1999, when Virtanen was describing the effect of snow cover on the residual gravity at Metsahovi. He showed a figure of gravity increasing by about 2 microgal over a 4-h period as men shoveled snow from the roof of the SG station, when a member of the audience asked why there was an interruption in the rise of gravity, Heikki said this was a 'tea break'...” D. Crossley, in Journal of Geodynamics 38/3-4 (2004), p. 234.