During the next 12 hours rapid development took place. The upper level trough sharpened and a closed circulation formed. The surface low pressure began to deepen rapidly while it moved from north Sweden to west Finland and further towards south-east Finland. The intensive Wave development led to occlusion by the early hours of 30 January. The accompanying snowfall with the passage of the Occlusion was quite intensive, especially in south-east Finland, as will be shown later. The most notable weather events were observed, however, only later during 30 January (compare Diagnosis of precipitation patterns with help of the relative streams and NORDRAD radar composites).