when i have had the same problem, it was exactly this...it rained like crazy here but not at the station. pretty typical here in my area, we will get .5 inch of rain about 100 yards to my north west, but not here. i could switch to a different weather station but looking at the histories of my local stations i still feel the one i have chosen is the better of the 4.
which is why im all kinds of fired up about the new ifttt events you all are adding.
i suggest an external rain sensor and an ifttt rule to impose a 24/48 hour rain delay if it trips as that will handle some valid/natural anomalies. my sensor is set to ~1/8th inch rain and that is where my weather intelligence is set as well so i feel secure with imposing an artificial restriction.
personally, it the complexity was not approaching "np", i would like the sensor tripping to impose a configured amount of percip in the system for my area when computing felxies. but that will cause the code to grow bat shit crazy in a hurry....