Just took a quick look at this one (busy around the holidays) and Merry Christmas...
Looks like a filter change or upgrade and/or relocation at the Tucson station...
Weather may have played a role as the winds are usually moving pretty good (lots of very small particles around there you know) and it looks like surface conditions may have stopped (or at least slowed) the local winds for a short while.
See image below.
The reads out of Phoenix kinda back up the wind theory.
It is somewhat of a mystery without doing some more research but the counter (Tucson) was obviously breaking in after a upgrade, filter change and/or relocation...
The history for Tucson shows a VERY wide variation. Click on 1 month and 1 year average in the chart history and look at the highs and lows.
If I had to guess (and this is a pure guess) I would say they are working to get a better (more accurate and readable) detection from this station so let's all watch it for a few days and see what happens after the break in...
Keep a eye on it and contact me anytime you see anything strange at
rads@lamarsworldmall.comhttp://lamarsworldmall.com/weather