This study revises the surface layer formulation in the Weather Research and Forecasting (WRF) model to improve its performance in simulating atmospheric conditions, particularly under strong stable and unstable conditions. The revisions include two main sets of modifications: 1. **Similarity Functions**: The Monin-Obukhov similarity theory is used to calculate surface turbulent fluxes, and the current Kansas-type similarity functions are replaced with those proposed by Fairall et al. (1996) for highly unstable conditions and Cheng and Brutsaert (2005) for highly stable conditions. This extension allows the model to cover a broader range of atmospheric stabilities. 2. **Variable Limits**: The limits imposed on certain variables, such as the friction velocity \( u_* \), are reduced or removed to avoid undesirable effects. These changes aim to create a less restrictive and more consistent surface layer formulation. The impact of these changes on surface fluxes, near-surface meteorological variables, and planetary boundary layer (PBL) dynamics is analyzed. The revised scheme produces more efficient turbulent fluxes during the day and less efficient ones at night, leading to a sharper afternoon transition in the PBL. The near-surface diagnostic variables, such as wind speed, temperature, and specific humidity, show significant improvements, particularly at observational sites in the Iberian Peninsula. The new formulation also reduces the diurnal amplitude bias in wind speed and improves the agreement with observed values, demonstrating its effectiveness in simulating complex terrain and atmospheric conditions.This study revises the surface layer formulation in the Weather Research and Forecasting (WRF) model to improve its performance in simulating atmospheric conditions, particularly under strong stable and unstable conditions. The revisions include two main sets of modifications: 1. **Similarity Functions**: The Monin-Obukhov similarity theory is used to calculate surface turbulent fluxes, and the current Kansas-type similarity functions are replaced with those proposed by Fairall et al. (1996) for highly unstable conditions and Cheng and Brutsaert (2005) for highly stable conditions. This extension allows the model to cover a broader range of atmospheric stabilities. 2. **Variable Limits**: The limits imposed on certain variables, such as the friction velocity \( u_* \), are reduced or removed to avoid undesirable effects. These changes aim to create a less restrictive and more consistent surface layer formulation. The impact of these changes on surface fluxes, near-surface meteorological variables, and planetary boundary layer (PBL) dynamics is analyzed. The revised scheme produces more efficient turbulent fluxes during the day and less efficient ones at night, leading to a sharper afternoon transition in the PBL. The near-surface diagnostic variables, such as wind speed, temperature, and specific humidity, show significant improvements, particularly at observational sites in the Iberian Peninsula. The new formulation also reduces the diurnal amplitude bias in wind speed and improves the agreement with observed values, demonstrating its effectiveness in simulating complex terrain and atmospheric conditions.