GREENSBORO, N.C. -- Have you ever stepped outside into a very light rain or drizzle, proceeded to check the radar and find that there isn't anything showing up on the radar? No, the radar isn't broken! This precipitation is literally flying under the radar. This is a fairly common occurrence in the Triad especially during the fall months.
To explain why this happens it must be explained that the radar beam is titled up at a 0.5° angle. This is done so that the radar beam can 'see' most of the precipitation that develops in the clouds above the earth's surface. One of the side effects of having this 0.5° tilt is that as the beam gets farther away from the radar site it becomes increasingly higher above the ground.
As is the case sometimes in the Triad there is a shallow layer of moist air that mixes with a shallow layer of cool air. The interaction between these two different air masses causes drizzle or light rain to develop very close to the ground. Due to the low altitude of the light precipitation often times the radars are not able to 'see' this low level precipitation.
WFMY News 2