  The spectra of disc-dominated cataclysmic variables (CVs) often deviate from
the spectra of accretion disc models; in particular, the Balmer jump and
absorption lines are found to be shallower in the observations than in the
models. We carried out a combined ultraviolet-optical spectral analysis of two
dwarf novae: UZ Ser in outburst, decline, and quiescence, and CY Lyr on the
rise to outburst and in outburst. We fit the Balmer jump and absorption lines,
the continuum flux level and slope by adjusting the accretion rate,
inclination, and disc outer radius. For both systems we find an accretion rate
$\dot{M} \approx 8 \times 10^{-9}M_\odot$/yr in outburst, and $\dot{M} \approx
2-3 \times 10^{-9}M_\odot$/yr for the rise and decline phases. The outer disc
radius we derive is smaller than expected ($R_{\rm disc} \approx 0.2a$, where
$a$ is the binary separation), except during late rise (for CY Lyr) where
$R_{\rm disc}=0.3a$. UZ Ser also reveals a 60,000~K white dwarf. These results
show that during a dwarf nova cycle the radius of the disc is the largest just
before the peak of the outburst, in qualitative agreement with the disc
instability model for dwarf nova outbursts. We suspect that an additional
emitting component (e.g. disc wind) is also at work to reduce the slope of the
continuum and size of the Balmer jump and absorption lines. We stress that both
the outer disc radius and disc wind need to be taken into account for more
realistic disc modeling of CVs.
