Using Spherics
Both spherics and NEXRAD have blind spots and neither is infallible. Spherics devices can have false negatives because they dont see those static discharges until they happen. While most cells with dangerous opposing currents also produce significant static, nature is inherently unpredictable and the static discharges can lag. Of course, the delays in getting NEXRAD images to the cockpit can lead to significant errors. Plus, radar only seeing precipitation, not turbulence, can cause difficulty interpreting the image.