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. . . . . Ie . . . (I . . . . . . . . . . . . . . . .' . . . . . . . . . . .. . . . . . . expects snow accumulations of four inches or more per 12-hour period or six inches or more per 24-hour period. . Winter Storm Warning (WSW) - This is issued by the NWS when it expects sudden drops in surface temperatures and heavy snow with significant blowing and drifting. . Flash Flood Warnings (FFW) - This is issued by the NWS in the event of heavy rainfall rates (1/4 inch per half hour) associated with slow moving (less than 10 knots) precipitation radar echoes, or radar echoes moving parallel to specific drainage areas. FFW are generally issued, but not limited to, spring and summer convective systems. In advance of the above described weather warnings, the NWS at times may issue weather "watch" bulletins. These "watches" delineate specific areas where atmospheric conditions are favorable for the formation of possibly hazardous weather phenomenon and are generally issued 12-hours in advance ofthe potential event. NA WC's Suspension Procedures NA WC's suspensIOn policy concerning Traveler's Advisories, Heavy Snow Warnings and Winter Storm Warnings is based upon the intent of its weather modification operations. In that regard, winter orographic seeding is conducted for and limited to increases in snowpack in the high runoff yield areas (i.e., high elevations). Therefore, such operations would not adversely affect driving conditions in the valleys. Additionally, the arnount of snowfall increases from seeding alone, in mountainous terrain, is not envisioned to produce heavy snowfall (that is, the heavy snowfall conditions would be present without seeding). Concerning Winter Storm Warnings the same reasoning for TA's applies, III 27