Whereas the ABL depth variability on diurnal, intra-diurnal, synoptic and seasonal time scales is well documented, changes in ABL processes, before, during and after frontal passages or ABL depth variability as a function of weather patterns largely remain unexplored. To understand the frontal modification of ABL features, we explored 5-years (2014-2018) of rawinsonde observations over 17 sites located in the central and eastern US. While selecting sites for this study from the IGRA (Integrated Global Radiosonde Archive) database, we confirmed that the sites were not affected by inflow of urban boundary layer airmass, coastal flow advecting marine boundary layers, and terrain-modulated elevated mixed-layers. Thus, all the sites chosen were far from the sources of different air mass (i.e., urban boundary layers, elevated mixed-layers over mountains, and marine boundary layers). We will present selected results obtained from analyses investigating ABL depth changes during warm and cold front passages in four seasons determined using more than 17,000 rawinsonde profiles and 14,000 surface map analyses. We will also compare our findings of ABL depth variability observed during frontal passage cases versus typical fair-weather anticyclonic conditions. The knowledge gained from this work will advance our understanding of moist boundary-layer processes and single out potential sources that trigger drastic changes in ABL dynamics during, before, and after frontal passages.