The current and forecast composite water anomaly index for the contiguous United States continues to indicate numerous regionally significant anomalies. This information is based on observed temperature and precipitation data through August 2015 and forecasts issued the last week of 2015.
The most notable impacts have occurred in the West. Wildfires have burned 8 million acres, snowpack in the Sierra Nevada Mountains is at a 500-year low, and exceptionally warm waters and low river flows in the Pacific Northwest have devastated fish hatches.
- September 2017
- August 2017
- July 2017
- June 2017
- May 2017
- April 2017
- March 2017
- February 2017
- January 2017
- December 2016
- November 2016
- October 2016
- September 2016
- August 2016
- July 2016
- June 2016
- May 2016
- April 2016
- March 2016
- February 2016
- January 2016
- December 2015
- November 2015
- October 2015
- September 2015
- August 2015
- July 2015
- June 2015
- May 2015
- April 2015
- March 2015
- Water deficits may dominate the northern US from the Pacific Northwest through the Great Lakes region.
- California may transition from deficits to moderate surpluses, with both surpluses and deficits possible in Northern California.
- Moderate deficits are forecast for Louisiana, Mississippi, and Alabama.
- Surpluses are expected in the Central and Southern Plains, in the Mid-Atlantic, and in Florida. Surpluses in the Southern Plains may be exceptional and widespread.
- The US Southeast may have characteristics of both water deficits and surpluses.
The 3-month composites (below) for the same 12-month period show the evolving conditions in more detail. Of particular interest is the possible emergence of extensive deficits forecast March through May from the central Gulf Coast region northward through the Great Lakes region. (It should be noted that forecast skill declines with longer lead times.)
September to November:
- Deficits may persist in the western US, though the Pacific Northwest may experience both deficits and surpluses. Deficits may also persist in the Northern Plains and into Minnesota.
- Surpluses may persist in the Central and Southern Plains and along Mississippi River tributaries; and may emerge in northern Mississippi, northern Alabama, and eastern Tennessee.
- Deficits in the Southeast may transition to surpluses in November.
- Deficits may emerge in Upstate New York, Massachusetts, Connecticut, and Rhode Island, but may subside by November.
December through February:
- California may transition from deficits to surpluses.
- Surpluses may dominate many parts of the country, with the exception of the Northern Plains, where deficits may persist. Tributaries of the Mississippi River may continue to experience surpluses.
March through May:
- Widespread deficits are expected to emerge in the Mississippi Valley from the Gulf of Mexico northward into the Canada, and in the Midwest and Great Lakes.
- Surpluses may continue to emerge in the West, Southwest, and Texas.
- Surpluses may also persist in the South Atlantic states, with particular severity in southern Florida.