Drought information statement
by National Weather Service Riverton, Wyoming
October 30, 2016
Moderate to severe drought eliminated across most of north central and northwest Wyoming since the end of summer.
The latest drought monitor released on October 20th showed significant improvement across northern Wyoming since late summer. Moderate /d1/ to severe /d2/ drought conditions across the northwest and most of the Bighorn Basin at the end of August had been eliminated for the most part in mid-October. The bighorn basin average precipitation for September of 2.75 inches was the 11th wettest on 123 years of record (since 1895). The Powder and Tongue River Basins had their 4th wettest September in 123 years with a basin-wide average of 2.86 inches.
Moderate /d1/ drought conditions remained over the Beartooth Pass area while most of northwest Wyoming and the northern Bighorn Basin had improved from moderate to severe drought to abnormally dry /d0/ conditions since the beginning of autumn. The only area in Wyoming to see worsening conditions since September 20th was northern Carbon County which is now Abnormally Dry.
Summary of impacts:
River and streamflow conditions
28 day average streamflows across Wyoming showed normal to above normal conditions at most locations. Any below normal conditions were isolated throughout the state.
Fire weather impacts:
Several wetting precipitation events during September extinguished the large wildfires that erupted across northwest Wyoming. Yellowstone National Park had 22 fires that burned more than 62,000 acres during the summer. Several wetting precipitation events along with longer nights and shorter days also resulted in fuels moistening up across most of the area, unlikely to carry large fires. However, most of Johnson and Natrona county's fuels remained classified as critical into mid-October.
Below are the cumulative precipitation amounts from selected locations across west and central Wyoming for the 2015-16 water year.
Note: basin-wide percent of averages are based on 20th century (1901-2000) averages. Specific locations percent of averages are based on 1981-2010 normals.
Information below shows:
Location and Drought Condition
Precipitation (Inches) for October 2015 – September 2016
% of Average
Yellowstone Basin Avg., 23.77, 86
0 Old Faithful, 20.44, 81
Snake Basin Avg., 30.95, 93
Afton, 17.65, 97
Moose , 20.67, 95
Green And Bear Basin Avg., 15.30, 112
Big Piney Airport, 10.28, 159
0 Evanston Airport, 6.71, 55
Fossil Butte N.M., 14.44, 131
Green River , 15.32, 184
Rock Springs (Fire Dp), 14.94, 155
Bighorn Basin Avg., 14.93, 99
0 Cody, 12.33, 117
0 Greybull Airport , 6.14, 82
0 Powell Field Station, 6.04, 89
Thermopolis, 14.03, 120
Worland Airport, 7.73, 115
Powder/Tongue Basin Avg., 14.40, 94
Buffalo Airport, 10.81, 80
Kaycee, 11.59, 94
Sheridan Airport, 15.37, 109
Lower Platte Basin Avg, 16.51, 111
Casper Airport, 16.42, 131
Cheyenne Airport, 17.49, 110
Wind River Basin Avg., 16.97, 114
Dubois, 11.18, 113
Lander Airport, 20.48, 162
Riverton Airport, 13.11, 139
Riverton (Downtown), 13.47, 160
Upper Platte Basin Avg., 14.00, 106
Jeffrey City, 12.12, 120
Statewide Average, 16.26, 102
The November outlook for Wyoming shows above normal temperatures are favored across the entire state with the greatest likelihood of above normal temperatures across the southern one-third of the state. The November outlook for precipitation shows an elevated chance of above normal precipitation across the northern half of Wyoming with equal chances of above normal, normal or below normal precipitation across the southern half of the state.
The November-December-January outlook for Wyoming shows an elevated chance of above normal temperatures across roughly the southwest half of the state with the greatest likelihood of above normal temperatures across Sweetwater, Uinta and southern Lincoln counties. The three month outlook for precipitation shows above normal precipitation is favored across most of the state with the greatest chance of above normal precipitation across north central Wyoming.
The seasonal drought outlook showed drought conditions were likely to end or improve by the end of February in the remaining areas across northern Wyoming currently classified with moderate or severe drought.
La Nina watch has been issued. La Nina is favored to develop (approximately 70 percent chance) during the northern hemisphere fall 2016 and slightly favored to persist during winter 2016-17. For Wyoming and the northern Rockies, the winter outlook (Dec-Feb) weighted toward this likelihood of La Nina conditions, favors above normal precipitation across northern and central Wyoming with the greatest likelihood of above normal precipitation across most of Montana into northern Yellowstone National Park and the Beartooth Pass area.
Hydrologic summary and outlook
Reservoir storages across Wyoming were in relatively good condition for September and early October. Notable exceptions were Palisades Reservoir (6 percent full) and Glendo Reservoir (34 percent full).
Reservoir data for October 20, 2016
Reservoir Percent Full
Buffalo Bill, 65.0
Bull Lake, 16.7
Upper Green River Basin
Big Sandy, 41.0
Flaming Gorge, 85.0
Upper Snake River Basin
Grassy Lake, 82.0
Jackson Lake, 54.0
Related web sites:
Additional information on current drought conditions may be found at
the following web addresses (use lower case letters):
To report effects of the drought in your area, please go to the
drought impact reporter at: http://droughtreporter.unl.edu/ and click on submit a report.
Information for the media may be found at:
NWS Riverton Drought page
Wind River Indian Reservation and surrounding area climate and
USGS Wyoming Drought Watch
U.S. Drought Monitor
NOAA drought page
Climate Prediction Center /CPC/
Additional river and reservoir information:
NWS Advanced Hydrologic Prediction Service /AHPS/
Water Resource Data System (WRDS)
The drought monitor is a multi-agency effort involving NOAS’s National Weather Service and National Climatic Data Center, the USDA, State and Regional Center climatologists and the National Drought Mitigation Center. Information for this statement has been gathered from NWS and FAA observation sites, State Cooperative Extension Services, the USDA, USACE and USGS.
For more information contact:
Climate/Drought Focal Point
National Weather Service
12744 West US Highway 26
Riverton, WY 82501