Drought Information for Southern Nevada, Southeast California and Northwest Arizona
Moderate to extreme drought conditions continue across the area.
Drought Information Statement
The Drought Information Statement is a summary of
the current state of the drought, including precipitation deficits, local impacts, outlooks, and other information. A statement is issued only when extreme drought (D3) or higher is occurring within the National
Weather Service in Las Vegas' area of responsibility.
Current Drought Monitor
The U.S. Drought Monitor was established to assess drought severity in a subjective
but uniform manner. Since 1999, various agencies, including those within the U.S. Department of Agriculture (USDA) and the
National Oceanic and Atmospheric Administration (NOAA),
have pooled their expertise with that of academia and local interests to more accurately categorize drought. Incorporating the input of all these entities, the National Drought Mitigation Center (NDMC)
issues a weekly assessment of drought severity on a national scale. To learn more about the U.S. Drought Monitor check out this brochure. Click the image below to enlarge.
Current Drought Indicies
Palmer Drought Severity Index
The Palmer Drought Severity Index is an index of the relative dryness or wetness affecting water sensitive economies. The Palmer Index was developed by Wayne Palmer in the 1960s and uses temperature and rainfall information in a formula to determine dryness. It has become the semi-official drought index. The Palmer Index is most effective in determining long term drought - a matter of several months - and is not as good with short-term forecasts (a matter of weeks). It uses a zero (0) as normal, and drought is shown in terms of minus numbers; for example, minus 2 is moderate drought, minus 3 is severe drought, and minus 4 is extreme drought. The Palmer Index can also reflect excess rain using a corresponding level reflected by plus figures; i.e., 0 is normal, plus 2 is moderate rainfall, etc. The advantage of the Palmer Index is that it is standardized to local climate, so it can be applied to any part of the country to demonstrate relative drought or rainfall conditions. The negative is that it is not as good for short term forecasts, and is not particularly useful in calculating supplies of water locked up in snow, so it works best east of the Continental Divide.
Crop Moisture Index
The Crop Moisture Index (CMI) is also a formula that was also developed by Wayne Palmer subsequent to his development of the Palmer Drought Index. The CMI responds more rapidly than the Palmer Index and can change considerably from week to week, so it is more effective in calculating short-term abnormal dryness or wetness affecting agriculture.CMI is designed to indicate normal conditions at the beginning and end of the growing season; it uses the same levels as the Palmer Drought Index.
It differs from the Palmer Index in that the formula places less weight on the data from previous weeks and more weight on the recent week.
Keetch-Byram Drought Index
The Keetch-Byram Drought Index is a drought index specifically for fire potential assessment.
It is a number representing the net effect of evapotranspiration and precipitation in producing cumulative moisture deficiency in deep duff (which is the organic material layer between the uppermost soil mineral horizon and the litter layer). It is a continuous index, relating to
the flammability of organic material in the ground.
Data and Other Information
Radar Precipitation Estimates
A complete suite of radar-estimated precipitation data is now available through the National Weather Service's Advanced Hydrologic Prediction Service. Images are available for month-to-date and year-to-date totals, among other selectable time frames. Menus below each image allow for user-customized data, including departure from normal.
Sample 180 Day Precipitation Map
Colorado River Water Supply Outlook
The Colorado River Water Supply Outlook is issued by the Colorado Basin River Forecast Center typically between January and June.
These maps from the Climate Prediction Center show the percent of pasture and range land in good and very good conditions as well as those in poor and very poor conditions.
These maps from the Climate Prediction Center show the calcualted soil moisture across the country for specific time periods.
Experimental Forecast Reference Crop Evapotranspiration (FRET)
These maps reference crop evapotranspiration shown here are the Forecast Reference crop EvapoTranspiration or FRET, and are presented as the most likely depth of water (in inches) that
would evaporate and transpire from a reference crop under the forecast weather conditions on a daily and weekly basis.
Drought Impact Reporter from the National Drought Mitigation Center
Drought severity is inherently linked to the impacts of the drought. Such impacts include agricultural issues, hydrologic deficits, increased fire danger, and other economic and social consequences. These impacts are not easily quantified with simple statistics.
The National Drought Mitigation Center developed the Drought Impact Reporter as a database for reported drought impacts. The impacts are classified by category, with the number of reports emphasizing a drought's significance without attributing specific statistics to the reports. (Click on a county of interest for further information.)
U.S. Seasonal Drought Outlook
This outlook from the Climate Prediction Center (CPC) predicts the future evolution of drought, including the potential for development or relief.
How Much Precipitation Is Needed To Return To "Near Normal"?
For areas currently in drought, the image below shows the amount of precipitation in inches that needs to fall in order to return to the "near normal" Palmer category. This is essentially how much precipitation needs to fall in order to end the drought across our area.
What Is The Outlook For Our Area?
CPC's 3-month outlooks present the likelihood of receiving a precipitation total that differs significantly from normal. For precipitation, green areas denote parts of the country with an increased chance of being in the wettest tercile, or the wettest third of historical data. Similarly, brown areas denote parts of the country that are projected to have an elevated chance of being in the driest tercile. Where neither color is shaded, CPC has concluded that there is no strong signal to determine an accentuated chance of being in either the driest or wettest tercile. This does not mean that near normal precipitation is expected, but simply that the 3-month period is just as likely to be in the wettest tercile as it is to be in the driest tercile.
Links of Interest
National Integrated Drought Information System
National Drought Mitigation Center
CPC's U.S. Drought Assessment
USGS Water Information for Nevada
California Department of Water Resources
Arizona Department of Water Resources
Arizona Drought Watch Page