One other thing - keep an eye on the Smith gauge. The Smith is often an early indicator for the Illinois. If they are getting hammered over there, it's likely the Illinois will catch a chunk of the rain as well. Keep in mind, the CNRFC website (CNRFC - Hydrology - River Guidance - Graphical RVF - CREC1
) does not update over the weekend, but USGS does. Sometimes the predictions show the Smith with a healthy bump but nothing on the Illinois (http://www.nwrfc.noaa.gov/station/fl...G&v=1447774460
). If that's the case there's still hope because if the storm misses a little to the west the drainages are right next to each other.
Another tool is to go to the Trip Reports page (Trip Reports | Oregon Rafting
) and filter by river. Most of the trip reports show what the USGS gauge was just before, during, and slightly after the trip. It can be helpful to see flow history for actual trips that have happened.
Hope that helps.