What a beautiful sunset tonight! I’m currently on Whidbey Island just north of Seattle, but Portland saw a spectacular sunset as well.
When the sun is low on the horizon like it is at sunrise or sunset, sunlight has to pass through more atmosphere before it reaches our eyes. The oxygen molecules in the atmosphere preferentially “scatter” out shorter wavelengths of light (such as blue and violet), so by the time the light reaches us, it is primarily red or orange.
Our best sunsets occur when we have clear skies to the west to allow sunlight to filter in, but clouds above to help reflect this light back to the surface. Altocumulus clouds are the best for sunsets because they are relatively high and reflective compared to lower, stratiform clouds, so they allow more light in and reflect more back to Earth. Unsurprisingly, the clouds over our area tonight are altocumulus (some might argue stratocumulus, but they are similar) clouds.
The old adage ‘red sky at night, sailors delight’ is one of the few meteorological sayings with some scientific validity, because a nice sunset means that there are clear skies to the west and any inclement weather is moving east of the area, and the weather in the midlatitudes comes from the west. As you can see in the satellite image below, skies well offshore are pretty darn clear apart from some very low fog/stratus hugging the surface of the Pacific.
However, it doesn’t always hold true, and it certainly won’t this weekend. Saturday will be much cooler than today with highs in the low 70s and thick morning clouds burning off in the afternoon, and we could even see a few showers on Sunday.
Hope you enjoyed the sunset, and have a great weekend!
