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<br />. <br /> <br />e <br /> <br />e <br /> <br /> <br />precipitation occurs as the bands approach the foothills. The <br /> <br />bands are highly variable in space and time and normally occur <br />along and ahead of the main front. Occasionally, bands occur in <br /> <br />a stable atmosphere. <br /> <br />3. Convective cells develop mainly behind the front and along <br /> <br />I <br />the lower foothills of the Sierra Nevada (near 1000 m, m.s.l). <br /> <br />They move up the barrier toward the crest parallel to but slightly <br /> <br />slower than the 700 mbar wind. As convective cells move from the <br /> <br />valley to the mountain, they tend to veer to the left of the steer- <br />ing winds. Convective cells which occur in a band tend to move <br /> <br />from south to north relative to the band. <br /> <br />4. Stable orographic clouds have been relatively rare during the <br /> <br />past two seasons. What casually appears to be a stable orographic <br /> <br />cloud, contains banded or cellular structure upon closer examination. <br /> <br />5. Multicells (clusters of cells) are frequently present in <br /> <br />Sierra Nevada storms and are generated by the merger of individual <br />cells. They normally move much slower then the steering wind and <br />at relatively large angles to the steering wind. <br /> <br />6. Seedable regions (low ice crystal concentrations and high <br />liquid water content) appear to be strongly localized. Such <br /> <br />regions appear to be associated with convection. Stable, <br /> <br />orographic clouds seem to have no seedable region unless it <br /> <br />1-9 <br />