Keys aims of LANFEX include: ?Improve understanding of fog formation and development controls, in terms of dynamics and radiative feedback; ?Evaluation and improvement of kilometre-scale and higher resolution MetUM simulations for fog and local boundary-layer evolution in general. Extensive observations, ending end of March 2016, are being made at sites in the shallow valley of the River Great Ouse around Bedford and deeper valleys in Shropshire. High-resolution MetUM numerical simulations and an ensemble of MetUM numerical simulations using MOGREPS-UK are being performed for these regions.