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<br />17 <br /> <br />not due to overlying cloud cover with the front, but to deeper clouds <br /> <br />due to convergence and thus increased processing of available moisture. <br /> <br />~ <br />. <br /> <br />Within the large frontal band, narrow bands of enhanced convection <br /> <br />~ <br /> <br />were seen (Figure 5). The band just on the southeast corner of the <br /> <br />target in this image affected mean CTT and Auburn and Blue Canyon pre- <br /> <br />cipitation at 1645 GMT. Another band to the north, partly covered by <br /> <br />cirrus, arrived at the project area near 1900 GMT. Forced by the upper <br /> <br />o <br />trough and not the surface front, this band's CTT approached -50 C. <br /> <br />Covered by smooth cirrus, the convective elements of the band were <br /> <br />hidden from satellite view. <br /> <br />The 9 March storm provided good observations of a cold frontal <br /> <br />passage through the Sierras. Observations of this storm clearly showed <br /> <br />~ <br /> <br />the decrease in CTT ahead of the front to a value below the lower boun- <br /> <br />o <br />dary of the seeding window (-25 C), during which most of the precipi- <br /> <br />~ <br /> <br />tation took place. Pre-frontal and post-frontal CTT of the orographic <br /> <br />cloud remained well within the seeding window, with the cap cloud dis- <br /> <br />sipating several hours after the frontal passage. Reynolds (1977) and <br /> <br />Reynolds and Morris (1978 a,b) include descriptions of the 9 March, <br /> <br />1977 storm. Radar observations of the storm are summarized in Sutherland <br /> <br />et al. (1977) and agree well with the satellite results. Radar observed <br /> <br />the frontal band merger into the orographic cloud and also detected the <br /> <br />post-frontal band within the target area as seen on the satellite image <br /> <br />at 1645 GMT. <br /> <br />, <br />