Weather Report for September 18, 2017

Most of the night was perfect, with photometric skies and seeing of around 1.5 arcsec. Plenty of blazars were observed up until 0400 local time. Then, the mountain decided that it was time to produce its own clouds as it has done during the past several nights. Fortunately, cloud production started with less than two hours left in the night. This is a very odd weather pattern since the entire state of Arizona looks to be clear on the satellite image. Similar weather is forecast for the coming nights and it can only be hoped that the timing of any orographic clouds will be late and after many blazar measurements have been made.