  Spectral fitting of the radio through hard X-ray emission of BL Lac objects
has previously been used to predict their level of high-energy (GeV - TeV)
emission. In this paper, we point out that such spectral fitting can have very
large uncertainties with respect to predictions of the VHE emission. This is
demonstrated with the example of W Comae. We show that the best currently
available contemporaneous optical - X-ray spectrum of W Comae still allows for
a large range of possible parameters, resulting in drastically different > 40
GeV fluxes. We find that all acceptable leptonic-model fits to the optical -
X-ray emission of W Comae predict a cut-off of the high-energy emission around
~ 100 GeV. We suggest that detailed measurements and analysis of the soft X-ray
variability of W Comae may be used to break the degeneracy in the choice of
possible fit parameters, and thus allow a more reliable prediction of the VHE
emission from this object. Using the available soft X-ray variability measured
by BeppoSAX, we predict a > 40 GeV flux from W Comae of ~ (0.4 - 1) * 10^{-10}
photons/(cm^2 s) with no significant emission at E > 100 GeV for a leptonic jet
model. We compare our results concerning leptonic jet models with detailed
predictions of the hadronic Synchrotron-Proton Blazar model. This hadronic
model predicts > 40 GeV fluxes very similar to those found for the leptonic
models, but results in > 100 GeV emission which should be clearly detectable
with future high-sensitivity instruments like VERITAS. Thus, we suggest this
object as a promising target for VHE gamma-ray and co-ordinated broadband
observations to distinguish between leptonic and hadronic jet models for
blazars.
