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Seasonal to Interannual Forecasts

Climate Outlook

ARCHIVE COPY - June 2007

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The Climate Impacts Group (CIG) translates global-scale climate forecasts and conditions into regional-scale climate forecasts for Pacific Northwest (PNW) resource managers and the general public. The El Niño/Southern Oscillation (ENSO) is the most important factor for seasonal forecasting, changing the odds for different types of winter and spring weather (e.g. warmer/drier, cooler/wetter) in the PNW. Another important climate variable for Pacific Northwest climate is the Pacific Decadal Oscillation (PDO). The climate outlook also provides the basis for natural resource forecasts, including the CIG's annual streamflow forecasts.

What's Next for the Pacific Northwest?

June 2007
Updated June 12, 2007 (posted 6.18.07)

The climate outlook is reviewed after the 20th of each month and updated as needed.

While southern Idaho was slightly warmer than normal in May, much of the Pacific Northwest (Idaho, Oregon, and Washington) experienced near normal temperatures. Temperatures along the coast continued to remain cooler than the 1950-2007 average (Jan.-May anomalies, May anomalies) despite anomalously warm sea-surface temperatures over the north central Pacific which continue to intensify and expand eastward. Precipitation for May was much below normal with most of the region receiving less than 50% of its average, due to a persistent ridge of high pressure located off the coast.

As of June 1, the only basins with snowpack are those in the higher elevations. The June 1st snowpack decreased by about 30% for most basins compared to May. Snowpack was 70-80% of normal in the Washington Cascades and southeastern British Columbia (Kootenay); 35-50% of normal in the Oregon Cascades and northern Idaho; and below 10% of normal in southern Idaho and eastern Oregon. The poor snowpack in Idaho and eastern Oregon is consistent with the above normal temperatures and below normal precipitation that have been observed since February, and will continue to stress water supplies in the region through the summer (Drought Monitor).

The Fraser and other rivers in British Columbia experienced flooding in early June as "an extended period of hot weather beginning the last week of May produced rapid snow melt and runoff" (Ministry of the Environment, Canada).

Current indicators for Pacific climate

El Niño/Southern Oscillation (ENSO). May equatorial Pacific sea surface temperatures (SST) were characterized by cold anomalies in the east which have increasingly become colder the last few months, but with persistent warm anomalies in the west, neutral conditions prevail in the central equatorial Pacific (relative to the 1950-2007 mean), where the correlation of SST and PNW climate is strongest. The current indications of the 14 models summarized by the IRI is for near normal to cool ENSO ("La Niña") conditions for this summer through next winter. Historically, the next few months are a favorable period for the development of La Niña conditions, so careful monitoring this summer should provide valuable guidance on the evolution of ENSO over the next year (CPC ENSO Discussion).

Pacific Decadal Oscillation (PDO). The PDO index value was small and negative in May with respect to the 1900-93 mean. NOAA's Earth System Research Laboratory is now producing experimental Pacific SST forecasts, including forecasts for the PDO index, at lead times of 3 to 12 months into the future. Details on methods and the forecasts are available here.

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What does the outlook mean for the PNW in coming months?

The Climate Prediction Center's outlook for June-July-August is for a greater than 33% chance of warmer than normal temperatures and below normal precipitation for the Northwest, except for Idaho where there is a 40% chance of below normal precipitation. In the absence of strong ENSO conditions, the CPC precipitation forecast has negligible skill. The forecasts should be interpreted as the tilting of odds towards general categories of conditions, and should not be viewed as a guarantee that the specified conditions will be realized.

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Pacific Northwest Resource Outlooks

Climate Prediction Resources

The links below provide access to the latest information on the current state of global and regional climate, as well as links to global and regional climate predictions.

The Current State of the Tropical Pacific

Predictions of Tropical Pacific and North Pacific Conditions

The Current State of the Globe

Current and Predicted U.S. Conditions

Pacific Northwest Conditions

State Climatologist Offices

Special Areas