First we can look at the mean monthly precipitation for the common period of record, 1997-2013; see the chart below. Not surprisingly, Keystone Ridge picks up more precipitation in every month, with an annual excess of 51% (15.8" vs 10.5") compared to the airport. However, the magnitude of the monthly differences is much larger in the warm and relatively wet season, both in absolute and percentage terms; almost three-quarters of the excess at Keystone Ridge occurs in May through September. June and August are the months with the largest absolute difference in mean precipitation amount, but the largest percentage difference is in May, when Keystone Ridge typically receives more than twice as much precipitation as the airport.
The smoothed daily climatology of precipitation amounts is shown in the next chart, below. An interesting feature here is the August peak in precipitation amounts for Keystone Ridge; the data from the airport do not show the same late-summer peak. This difference is also suggested by the monthly chart above: precipitation peaks in July at the airport, but August is just as wet on the ridge (although with a pronounced drop-off by late month).
Thirdly, we can consider the mean frequency of measurable precipitation - see the chart below. The frequency is also higher at Keystone Ridge throughout the year, but the relative differences in summer are not as great as for the total precipitation amounts.