Figure 12. FSS (top) and Bias score minus 1 (bottom) for surrogate severe predictions with 12–36 hour lead times for three versions of C-SHiELD initialized at 00Z. Heavy black outline corresponds to the combination of UH threshold (m2s-2) and smoothing radius (sigma, km) giving the highest FSS.
We also investigate if skillful prediction of severe weather is possible beyond the first forecast day. Figure 13 shows surrogate severe FSS for days 1 through 4 (hours 12–36, 36–60, 60–84, and 84–108, respectively). The FSS value is not as high on later days as on the first, but even on day 4 the FSS is still a respectable 0.74, indicating that there is skill in predicting severe weather multiple days in advance. These high skill scores may be partially due to the relatively large smoothing radius of 240 km.