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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />the AHS release. These ice nuclei presumably came from ground.bascd seedmg on the Utah <br />operational project, which had occurnng 40 to 60 miles to the south since midday on 7 February. <br /> <br />C. 10-11 February Storm Period <br />As the trough from stonn period B moved across the central U.S.. lhe flow over the western <br />U.S. lx.-came somewhat zonal \\oith \"'cst to west-northwesterly v,'iods bringing rather cold air oul of <br />the Gul f of Alaska, in contrast to the beginning of period B which began in wann southv.'csterly <br />flow. There v,'a.. some warm air advl.-ction o\'er Utah on 10 February. and brlcfridging ahead of the <br />next well defined upper air trough which was still offshore at 0500 on 10 February. Bet\\ieen 0500 <br />and 1700 the 700 mb air over Utah wJrmcd from -10010 - 60and a wdl defined region of moisture <br />advectcd over the research area ahead of the trough. Figure 12 shows a prefrontal cloud band <br />arriving over the Utah research area at 1100, and Fig. 13 shO\....s lhe 700 mb map for 1700 on 10 <br />February with the trough axis through the northwest comer of Nevada and 3" dew point depression <br />air covering northern Nevada, Utah and southern Idaho. Winds over Utah had shifted to the wcst- <br /> <br />s()uthwest, and increased from 10 m s'. to 15 m S.l over the preceding 12 hours. <br />r "J f I </ -... <br />'" ' ,,~ 71 __ ;"'- <br />..... . - \ <br />... "j./ "} .!. <br />__ l. <br />i -- <br /> <br />+ <br /> <br /> <br />-- <br /> <br />L <br /> <br />Fixure 12. GOF:L~ IN Image laken 01 1100 lvIST on 10 February 199.J. <br /> <br />21 <br />