Note that the chart shows the synoptic situation at 1200 and the TAF starts at 1000.   At 1000 LOWW would have been in the warm sector and the TAF indicates typical warm sector weather; visibility 6,000m and 3 -4/8 at 3,000ft.   The TEMPO 1113 marks the passage of the cold front and the BCMG 1315 brings in typical cold sector conditions with good visibility and showers.