There are 5 major indicators (with one minor indicator) identified with chemtrail spraying - you can look for to know in advance spraying will occur.

Spraying Period #1: Around Full moons (possibly to cause mental confusion and mistrust among human populations)
Link Courtesy of Old Farmers Alamac: http://www.almanac.com/moon/full/CA/Santa%20Monica

Spraying Period #2: When there are between 4 and 8 "C" Class Flares.

Spraying Period #3: When the X-Ray background Flux Levels reach 4.0 (possibly to block evolving consciousness)
Forecast Link Courtesy of NASA: http://www.swpc.noaa.gov/ftpdir/latest/DSD.txt

Spraying Period #4: During Certain Geomagnetic Storm Periods (possibly to alter or interferre with DNA of living organisms)
Forecast Link courtesy of Northwest Research Space Weather:
http://www.nwra.com/spawx/27do.html

Spraying Period #5:

3 consecutive days or more of Rising Solar Flux with a forecasted solar wind speed “jump”

Solar Wind Forecast Link courtesy of LMSAL (palo alto, ca)
http://www.lmsal.com/forecast/wind.html

Solar Flux Forecast Link courtesy of Space W.com
http://www.spacew.com/www/dailyrpt.html

Spraying Period #6 (minor)

The changing of our suns polarity (which occurs on average every 8 days)
BZ Forecast and prediction Courtesy of NOAA
http://www.swpc.noaa.gov/ws/index.html

I have outlined the cycles "condition green" and the other condition blue. To keep it simple, one of the main points to look for is when there are between 4 and 8 "C" Class solar flares, which is the time that the body and human consciousness is most stimulated. This stimulation creates an alternate reality when the solar wind "jumps". Also the Xray background flux levels usually are either dropping or rising for 3 or more consecutive days. Click the image for a larger view.

Lastest Los Angeles Chemtrail Spraying Reports

December 27th. No Spraying Today

Dec 28th. No Spraying Occured This Day

-----------------------------------------------------------------------------------------------------------------------------------------------------

Los Angeles Future Chemtrail Spraying Forecast

Cycle #4.

Chemtrail Spraying forecast between December 30^th, 2011 and January 1^st, 2012 with 70% Confidence.

Chemtrail Spraying forecast between January 5^th and January 7^th, 2012. 90% Confidence.