Observational evidence of the influence of Pacific SSTs on winter precipitation and spring stream discharge in Idaho

Forty years of winter precipitation (23 stations) and spring stream flow discharge records (five stations) from across Idaho are analyzed to reveal regional patterns of association with sea surface temperatures (SSTs) in the Pacific Ocean. Results indicate that winter precipitation in the northern Idaho mountains, between 45° and 48°N, is negatively correlated with fall SSTs in the eastern tropical Pacific Ocean (El Nino and La Nina). Winter precipitation north of 45°N, is negatively correlated with winter SSTs in the northern Pacific (Pacific Decadal Oscillation, PDO). Spring stream discharge in Idaho is also negatively correlated with SSTs in the eastern tropical and northern regions of the Pacific Ocean. The association is asymmetric with stronger responses during negative SSTs for both regions in the Pacific Ocean. Wet and dry conditions are most likely associated with the combination of La Nina–negative PDO and El Nino–positive PDO, respectively. The greatest anomalies occur during the optimal combination of La Nina with negative PDO conditions. The revealed connections are valuable for climatic predictions based on the previous seasonʹs SST conditions in the eastern tropical Pacific and slowly evolving SSTs in the northern Pacific Ocean.