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Tower observation is more accurate than ATIS. If the ATIS is reporting below 1sm and the tower says it is 5sm, you can go. The controller hasn't had time to change the ATIS yet, but he will soon. Same when flying IFR, the ATIS is reporting vis below 1/2sm for the ils, but if the tower tells you the vis is 3/4sm, you are legal to start the approach and land.
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Remember ATIS only changes when there is official weather. This is usually once an hour or if conditions change rapidly warranting a SPECI observation. When tower is calling out RVRs or visibility, that is the current condition and you can fly the approach.