TAF VTBD 271800Z 2800/2824 VRB05KT 1200 BR TEMPO 2800/2802 4000 BECMG 2802/2805 9999 NSW SCT015 BKN100 TEMPO 2811/2818 04010G20KT 4500 TSRA SCT009 BKN014 BKN018CB BECMG 2820/2824 4000=

Period of validity is stated as 00:00 UTC day 28 until 24:00 UTC day 28 (2800/2824).
Initial weather conditions are forecasted to be:

• VRB05KT = wind variable at 5 kt
• 1200 = visibility 1200 m
• BR = mist

Next changes expected are of temporary character (TEMPO 2800/2802) => which means that the listed conditions can occur on day 28 at any time between 00:00 and 02:00 UTC, but are not of permanent character and may occur momentarily, for a max of 1h at each time. Thereafter, the conditions will revert back to how they were previously.

• 4000 = visibility 4000 m

A change of permanent character is expected to occur on day 28 at any time between 02:00 and 05:00 (BECMG 2802/2805). After the change occurs, the following conditions are to be expected:

• 9999 = visibility 10 km or more
• NSW = no significant weather
• SCT015 = scattered clouds at 1500 ft
• BKN100 = broken layer at 10 000 ft

Next changes expected are of temporary character (TEMPO 2811/2818) => which means that the listed conditions can occur on day 28 at any time between 11:00 and 18:00 UTC, but are not of permanent character and may occur momentarily, for a max of 1h at each time. Thereafter, the conditions will revert back to how they were previously.

• 04010G20KT = wind 040º at 10 kt gusting to a maximum of 20 kt
• 4500 = visibility 4500 m
• TSRA = thunderstorms and moderate rain
• SCT009 = scattered clouds at 900 ft
• BKN014 = broken layer at 1400 ft
• BKN018CB = broken layer at 1800 and Cumulonimbus

Another change of permanent character is expected to occur on day 28 at any time between 20:00 and 24:00 (BECMG 2820/2824). After the change occurs, the following conditions are to be expected:

• 4000 = visibility 4000 m

=> At 1400 UTC, we might be affected by the change of permanent character occurring between 02:00 and 05:00 UTC => visibility 10 km or more or the change of temporary character occurring between 11:00 and 18:00 UTC => visibility 4500m. However, the lowest forecasted visibility is the lowest of both forecasts (because question does not ask for most likely). Hence, correct option 4500 m.