Precipitation for May was much below normal across the State. Year-to-date precipitation is generally well below average for the State. Precipitation ranged from 15 to 42 percent below average, with all of the basins receiving below average. Reservoir levels vary from about 58 percent of average to 150 percent of average. Generally, the larger capacity reservoirs are above average storage. Forecast runoff varies from 9 to 73 percent of average. The mean of all the forecast points in the State is about 55 percent of average.
Snowpack
SWE is much below average for the entire State. Nearly all the SNOTEL sites have melted out.
Precipitation
May precipitation was much below average across the State. Nearly half of the State reported near 50 percent of average or less for the month. The southwest portion of the State received the least precipitation in percent of average, along with the Big Horn Basin in north central Wyoming. The following table displays the major river basins and their departure from normal for this month.
Basin | Departure from normal | Basin | Departure from normal |
Snake River | -37% | Upper North Platte River | -33% |
Yellowstone & Madison | -26% | Lower North Platte River | -15% |
Wind River | -36% | Little Snake River | -62% |
Bighorn | -61% | Upper Green River | -47% |
Shoshone & Clarks Fork | -39% | Lower Green River | -67% |
Powder & Tongue River | -49% | Upper Bear River | -68% |
Belle Fourche & Cheyenne | -48% |
Streams
Stream flow yield is expected to be below average across most of the State, and well below average in the northern half of the State. Most probable yield for the State is forecast to be about 41 percent of average (varies from 9 to 73 percent of average). The northwest part of the State is expected to yield about 40 percent of normal -- yield estimates vary from 18 to 53 percent of normal through the northwest region of the State. Yield from the northeast portion of Wyoming will be below average (about 26 percent of average) -- yield estimates vary from 9 to 42 percent of average for the various forecast points. The southeast portion of the state will be about 50 percent of normal -- yield estimates range from 34 to 73 percent of normal. The southwest portion of Wyoming yield will be much below normal (about 42 percent of average), and estimates vary from 19 to 66 percent of average.
Reservoirs
B A S I N W I D E R E S E R V O I R S U M M A R Y FOR THE END OF MAY 2001 BASIN AREA CURRENT AS LAST YR AS AVERAGE AS CURRENT AS CURRENT AS RESERVIOR % CAPACITY % CAPACITY % CAPACITY % AVERAGE % LAST YR -------------------------------------------------------------------------------- ALCOVA 98 98 98 100 100 ANGOSTURA 94 98 96 98 96 BELLE FOURCHE 103 107 85 121 97 BIG SANDY 51 86 74 69 59 BIGHORN LAKE 62 70 63 98 89 BOYSEN 69 91 92 76 76 BUFFALO BILL 63 78 58 108 81 BULL LAKE 52 74 61 86 70 DEERFIELD 99 99 89 111 100 EDEN 24 45 66 36 53 ENNIS LAKE 89 78 87 102 114 FLAMING GORGE NO REPORT FONTENELLE 46 54 57 81 85 GLENDO 88 100 99 89 88 GRASSY LAKE 97 94 89 108 103 GUERNSEY 78 79 76 103 99 HEBGEN LAKE 92 94 82 113 98 JACKSON LAKE 90 100 64 140 90 KEYHOLE 88 91 59 150 97 PACTOLA 99 99 88 112 99 PALISADES 60 95 75 80 64 PATHFINDER 78 98 63 125 80 PILOT BUTTE 47 78 81 58 60 SEMINOE 74 90 54 136 82 SHADEHILL 96 69 84 113 138 VIVA NAUGHTON RES 101 107 80 126 95 WHEATLAND #2 62 82 55 112 75 WOODRUFF NARROWS NO REPORT GLENDO PROJECT USERS 94 94 82 115 100 KENDRICK PROJECT 78 87 70 112 75 NORTH PLATTE PROJ 84 100 86 99 85