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Drought Impacts and Outlook Summaries - August 2016

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Highlights for the State

Statewide, July 2016 was the 9th driest July for the 122-year period of record and, for the Climate Division encompassing the Upper Platte, it ranked as the driest July out of the 122 years. The month ranked as the 39th warmest July for that same period.

Since mid-July, drought in the northeast has lessened some and extreme drought (D3) was reduced in Crook and Weston counties while severe drought (D2) was reduced in southern Campbell County. Moderate drought (D1) increased in northcentral WY to cover most of Big Horn County, northeast Park County, and western parts of Johnson County. Abnormally dry conditions (D0) expanded to cover all of Park County, the northern half of Lincoln County, and more of the western parts of Fremont and Sublette counties. D3 was introduced along the western flank of the Bighorn mountains northward to the MT border and westward into Park County.

In the south, D1 emerged briefly in eastern Goshen County. The D0 in the southeast portion of WY expanded to cover almost all of Converse, Goshen, and Platte counties as well as the northern and northeastern parts of Albany and Carbon counties respectively. Recently, the D0 improved in the border area between Platte and Goshen counties as well as in eastern Laramie County.

Although August rains have been beneficial for the Bighorn Basin and eastern quarter of the state, much of WY still needs moisture and fire potential remains above normal. Currently 17 fires are active in WY including five in Yellowstone NP and two in Grand Teton NP. Outside the National Parks, active fires exist in Park, Sublette, Fremont, Washakie, and Carbon counties.

Temperature and Precipitation Anomalies
Temperatures for the latter part of June through mid-August were above normal for most of Wyoming with the exception of the northwest where some stations were up to 2°F below normal. Most of the rest of Wyoming saw temperatures 1°F to 4°F above normal, with the highest anomalies in the northeast and parts of the southeast. For temperature, the eastern half of Wyoming was generally above normal while the western half was closer to or even below the normal range.

Most of Wyoming experienced well-below-normal precipitation between mid-June and mid-August. Almost without exception, departures from normal were negative with many stations being between 0.75" and 3" below normal. When looked at as a percentage of normal, most of the state was less than 70% of normal with much of that being less than 50% of normal. Northeast Wyoming (Crook, Weston, Converse, and Niobrara counties) was closer to normal with one station in Niobrara County being above normal.

Evaporative Demand
The Evaporative Demand Drought Index (EDDI) is a relatively new index used to monitor areas experiencing enhanced drying power of the atmosphere. The 2- and 4-week EDDI maps below show that the evaporative demand has been higher than normal over most of Wyoming over the past month, especially in Fremont, Park, Washakie, Johnson, and Sheridan. Do you have impacts to report? We need your on-the-ground reports and you can input them here: http://droughtreporter.unl.edu/map/

EDDI maps are updated on a daily basis for several timeframes. Current maps may be downloaded here: http://wwa.colorado.edu/climate/dashboard.html

Water Resources
Reservoirs statewide are in fairly good condition with a few exceptions, such as Palisades in the Snake River Basin (#<40% full) Streamflows in the Tongue, Yellowstone, Wind, and Upper Green basins were much below normal while most of the rest of Wyoming was normal to above normal.

The map below shows streamflow for August 18th compared to the historical average for this date.

Weather and Climate Outlooks
For the end of August (25-31 Aug) the chances are greater for below-normal temperatures except for far-west Wyoming and for above-normal precipitation statewide.

Looking farther out, the signals are less certain for precipitation. The Sep-Nov period has increased chances for above-normal temperatures statewide, but, for precipitation, most of the state has equal chances for above- or below-normal amounts with far-north Wyoming being more likely to see above-normal precipitation. This pattern continues into the Oct-Dec period for temperature, while precipitation is more uncertain though chances are for above-normal precipitation in the north and below-normal precipitation in the south. Moving to the Nov-Jan timeframe, above-normal temperatures are still favored for the southwestern two-thirds of Wyoming. It is more likely that the northern half of the state will see above-normal precipitation with the lower half being uncertain.

Drought conditions likely will persist in the north through August with some improvement being seen there over the next two to three months.

Summary of Conditions
August's temperatures have been much more moderate than July's. Only a few areas such as north-central Wyoming are running above normal. Precipitation has been below normal for much of the state so far this month, although eastern areas have seen some much-needed moisture. Central and north-central Wyoming have also had areas of above- normal precipitation. Drought has intensified in the northwestern and southeastern quarters of the state but has improved somewhat in the northeast.


Stay Tuned and In Touch
The next Wyoming Drought Impacts and Outlook Summary will be released around September 8th. If you need information in the meantime, please reach out to any of the partners listed to the right or contact Tony Bergantino directly at Antonius@uwyo.edu

Live in or around the Wind River Indian Reservation? Check out the Wind River Indian Reservation and Surrounding Area Climate and Drought Summary at: http://www.hprcc.unl.edu/pdf/WindRiver-Climate-Drought-Summary-Jun-16.pdf