Little change in drought conditions across Wyoming during the first half of August
by National Weather Service - Riverton WY
August 20, 2012
The latest US. drought monitor for Wyoming released on August 14th showed extreme drought /d3/ had expanded north across far eastern Wyoming into the southeast third of crook county. Drought conditions showed no change across west and central Wyoming from July 31st through August 14th. Moderate drought /d1/ or worse persisted across all but the northwest portion of the state...or roughly along and east of an Afton to Dubois to Cody line. Severe drought /d2/ or worse covered most of southern Wyoming and areas east of the continental divide. Extreme drought /d3/ remained across Sweetwater County into far southern Fremont county...and far eastern Lincoln and Uinta counties.
Extreme /d3/ drought continued to expand across eastern Wyoming.
Abnormally dry /d0/ conditions were observed across most of northwest Wyoming with the exception of northern Yellowstone National Park.
One year ago, Wyoming was 100 percent free of drought with a sliver of normally dry conditions across far eastern Wyoming. Abnormally dry /d0/ or moderate /d1/ drought conditions developed more rapidly through the spring after a below normal winter snowpack and a very warm and dry spring.
Wyoming had the second warmest July on record since 1895. July precipitation for the state was closer to normal after the driest June on record. The water year to date, October 2011 through July 2012, ranked as the 14th driest for Wyoming since 1895, and the driest since 2006. The dry spell began over most of the state in March, and the march-July 2012 period ranked as the second driest over the last 118 years with a statewide average of only 3.98 inches of precipitation. The driest March-July period was in 1919.
Worland had the driest March-July period on record with only 1.71 inches of precipitation. Rock Springs experienced the warmest and second driest march through July period on record with only 2.12 inches of precipitation.
Summary of impacts
River and streamflow conditions
USGS Wyoming drought-watch 28-day map of below average streamflow showed most river basins across central and southern Wyoming with below average streamflow.
Fire weather impacts
Fuels were classified as critical in all areas across west and central Wyoming. The seasonal significant wildland fire potential outlook for September through November 2012 showed normal significant fire potential persisting across west and central Wyoming. This potential remained above normal across most of west and central Wyoming for august. Significant fire potential is the likelihood that a wildland fire event will require mobilization of additional resources from outside the area in which the fire situation originates. Contact your local county officials for the latest burning restrictions.
Below are the cumulative precipitation amounts from selected locations across west and central Wyoming for the current water year.
Location | Water Year Precipitation To date (Oct 2011-July 2012) | % average (1981-2010)
^ BIG PINEY 2.34", 47%
^ BUFFALO 9.15" , 81%
* CASPER 9.32", 88%
* EVANSTON 2.98", 31%
* GREYBULL 4.40", 71%
^ LANDER 8.51", 77%
* RIVERTON 4.74", 60%
+ ROCK SPRINGS 4.89", 70%
^ SHERIDAN 12.32", 103%
* WORLAND 3.93", 62%
COOPERATIVE OBSERVER STATIONS
BEDFORD 3 SE 17.75", 96%
* BILLY CREEK 8.46", 81%
+ BITTER CREEK 4 NE 3.91", 72%
* FOSSIL BUTTE NAT MNT 7.21", 80%
+ GREEN RIVER 5.82", 86%
* JEFFREY CITY 5.20", 60%
MOOSE 15.65", 82%
OLD FAITHFUL 24.28", 108%
^ POWELL FIELD STATION 5.43", 96%
* RIVERTON (DOWNTOWN) 4.82", 72%
* THERMOPOLIS 6.13", 62%
+ location in extreme drought /d3/
* location in severe drought /d2/
^ location in moderate drought /d1/
The outlook for September shows a 40 percent or greater chance of above normal temperatures across most of Wyoming. The September precipitation outlook shows equal chances of above, below or normal precipitation, or no significant climate signal across most of the state.
The seasonal outlook for September, October and November shows a greater than equal chance for above normal temperatures all of Wyoming with the highest chances, a 40 percent or greater chance of above normal temperatures east of the Continental Divide. The seasonal precipitation outlook shows equal chances of
above, below or normal precipitation, or no significant climate signal across Wyoming.
The U.S. Seasonal Drought Outlook issued on August 16th showed that drought conditions were likely to persist or intensify through November across all areas in Wyoming that are currently in drought. Drought conditions are not currently forecast to develop in northwest Wyoming.
An El Nino watch has been issued by the Climate Prediction Center. El Nino conditions are likely to develop in August-September 2012 and continue through the winter of 2012-13. Enso-neutral conditions prevailed across the equatorial Pacific from May through July following the dissipation of La Nina in April.
Hydrologic summary and outlook
The following reservoir data was obtained on August 15th.
Central Wyoming Reservoirs
Boysen 74.7% full
Buffalo Bill 87.3% full
Bull Lake 86.0% full
Pathfinder 48.5% full
Upper Green River Basin Reservoirs
Big Sandy 35.0% full
Fontenelle 92.0% full
Flaming Gorge 82.0% full
Upper Snake River Basin Reservoirs
Grassy Lake 100.0% full
Jackson Lake 85.0% full
Drought Impact Reporter To report effects of the drought in your area. Click on Drought Impact Reporter to submit a report.
Information for the media
NWS Riverton drought page
USGS Wyoming Drought Watch
U.S. Drought Monitor
NOAA drought page
Climate Prediction Center
NWS Advanced Hydrologic Prediction Service