A sensor apparatus includes a sensor window; a first nozzle adjacent to the sensor window and oriented to blow across the sensor window, the first nozzle positioned below the sensor window and in a first horizontal direction away from the sensor window, the first nozzle being slot-shaped with a first length and a first thickness; and a second nozzle adjacent to the first nozzle and oriented to blow across the sensor window, the second nozzle positioned below the sensor window and in the first horizontal direction away from the sensor window, the second nozzle being slot-shaped with a second length and a second thickness. The second nozzle is farther from the sensor window in the first horizontal direction than the first nozzle, and the first length of the first nozzle is greater than the second length of the second nozzle.