CWCB Wintertime Weather Mod Report

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(, I I I I I I I I I I I I I I I I I I SUMMARY OF WEATHER AND OPERATIONAL SEEDING OPPORTUNITIES FOR THE 2002-2003 SEASON OF THE V AlL AND BEAVER CREEK SKI AREA CLOUD SEEDING PROGRAM November 2002 started out with a continuation of the wet weather trend started during the second half of October. Six weather systems over thirteen calendar days continued to maintain the above normal snowpack left by Octobers weather systems. Early indications were that this winter might be near or slightly above normal for snowpack and precipitation and allowed for earlier openings for most of the ski areas in Colorado. The trend of frequent weather systems moving through the Western U.S. increased through December bringing with it the occurrence of nine seeding opportunities over 21 calendar days into January 1, 2003. A subtle change was becoming apparent with these systems. The intensity and duration of each system was becoming slightly less as there was less southwesterly wind to bring in large amounts of moisture and most of the precipitation with these systems was occurring mainly in the higher elevations ofthe mountains. By the end of December, the snow pack in the Central Mountains had decreased to an average slightly under normal with several sites in the Seeding Area continuing tu I", no "buve normal I ""diu!;;.. - . - - - - - . . - . - -. - .,- The gradual drying trend of the weather system continued throughout January with shorter storm duration's for seeding operations. Six seeding opportunities occurred over 12 days in January. At the end of January, the high country snow pack in the Central Mountains had dropped to near 80% of normaL Most of the Seeded Area monitoring sites still indicating ail additional 15% greater snowpack and precipitation. At the end of January, the Vail region had received about 95% of its normal winter precipitation. During the 2002-2003 Operational Seeding Program, all of the estimated seeding hours were utilized for the Vail and Beaver Creek Ski Areas. Additional seeding hours were authorized when seeding opportunities existed during the last half ofJanuary when Vail and Beaver Creek's cost portion of the Seeding Program ended for this season. The Vail/Beaver Creek Operational Seeding Summary indicates the dates of all of this season's seeding operations, the number of and total seeding hours of the generators in the network that were used to seed the ski areas, the other generators in the network that were utilized or shared with the Vail/BC Program by the Denver or Upper Arkansas Program and their operating hours and the Total Output of Silver Iodide for each operation for the Vail/Beaver Creek Program., The Seeding Program over the Vail and Beaver Creek Ski areas was continued by the sponsors of the Denver Water Department Seeding program as the downwind seeding increases from this Program were beneficial to the adjacent and downwind Denver Seeding Program Area. Above normal precipitation and frequent weather systems with good seeding potential returned to the Central and Northern Colorado Mountains during February with 8 weather systems and 21 operational seeding days. Februarys snowpack increased so rapidly in the last half of February that an avalanche warning was issued. The average precipitation for the region had increased to about 90% of normal with many monitoring sites in the Seeded Areas indicating 10 to 15% more precipitation than adjacent unseeded sites. The wet weather trend continued into early March and then quickly turned very dry with warming temperatures. A very large slow-moving weather system moved into Colorado from the Southern California region in mid March and produced nearly continuous precipitation for about six days. This one system produced nearly half of the normal annual snowpack for the Eastern Slopes of Colorado and added about 10 to 15% to the spowpack in the central Rocky Mountain Region. A second weather system moved into Colorado from the northwest a few days later and contin~ed the mouf'kain ?re<;,1.?1.w.tion for another foor <!.a,s until the 11th of March. Se'ieral a'ialanche warnings were issued for the Northern, Central and the East-slope Mountain Ranges in Colorado during these