Total electron content (TEC) fluctuation in the ionosphere is one of the main unresolved problems degrading ambiguity resolution and thus affect the reliability of satellite positioning. With regard to conditions prevailing at mid-latitudes, the impact of the upper atmospheric layers is primarily associated with the occurrence of medium-scale traveling ionospheric disturbances (MSTIDs). This study contains the combined analysis involving MSTIDs patterns observed in raw phase data and their impact on rapid static positioning. The first part is aimed at discrepancies in wavelike MSTIDs signatures detected in time series of high elevated measurements. It was demonstrated that the differences in slant ionospheric delays at medium baselines often exceed 0.5 TEC units and more importantly, the detected MSTIDs patterns were highly mutable. The next section presents the impact of MSTIDs on double differenced ionospheric delays and performance of rapid static positioning. The positioning was executed using two approaches. The first one adopted as a benchmark strategy was the geometry-based relative positioning model with weighted ionosphere and troposphere parametrization. The second approach was the improved version of the former. It used the rate of TEC corrections, which allowed the mitigation of MSTIDs through the reduction of epoch-wise ionospheric delays to one parameter for each double-differenced arc. The comparison of results for both strategies indicated significant improvement of positioning performance after the application of proposed algorithm.