Last week I promised to give a heads-up if a
Pacific trough was coming through to provide a break
in the monsoon. This specifically in regard to observing
at the "Fredrickson Meadow" site up on the Rim. Rather
surprisingly, this has more-or-less happened overnight.
I expect that tonight will be possibly workable for
astro-viewing but with high humidity, while from Sunday night
onwards things will dry out considerably --- and might stay
that way for 10 days or two weeks.
Yesterday afternoon the various regional satellite
images looked a lot like the pattern of a Pacific trough
passage, but I could hardly believe it (and couldn't wrap
my mind around it). But apparently this was just what was
developing. The weather-obsessed will want to read the
NWS-Phoenix and Flagstaff forecast discussions,
linked for instance from:
http://www.wrh.noaa.gov/fgz/prod_list.php?wfo=fgz
...notably the Phoenix one dated 8:40pm Friday evening,
and the 9:55am Saturday morning one from Flagstaff,
both written by much more aware veteran forecasters.
\Brian
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