Northwest Outlook October 2016 Rainfall Opportunities and Challenges Rainfall over the month of September presented some challenges for the fall harvest while other producers benefitted. Figure 1a shows the last 30 days of rainfall expressed as a percent of normal and Figure 1b shows the forecast rainfall amounts in inches from Oct. 6 through 16. Here are the highlights: Heavy rains over Eastern Montana, Eastern Idaho and Western South Dakota have impacted the progress of the sugar beet and potato harvest. Rain during the first half of October will also impact: o The end of the potato harvest in the Columbia Basin and Northern Oregon. o Grape and apple harvest near Medford and the Willamette Valley through the Columbia Basin toward Yakima, Walla Walla and Wenatchee. o As of Oct. 6, the threat of a frost through the first half of October is very low. Dry land rainfall will be very beneficial to newly planted winter wheat. Pasture in the Pacific Northwest could really use this rain to revive growth, allowing cattle to stay out to pasture longer this fall. Warmer temperatures (especially overnight lows) forecast for the first half of October will prevent an early season frost for most locations that have yet to have a freezing temperature this fall. Forecast rainfall may challenge corn silage harvest efforts in the Columbia Basin and Northern Washington.
Figure 1a. Last 30-days (Sept. 6-Oct. 6) of precipitation expressed as a percent of average rainfall. Image Credit: Eric Snodgrass Figure 1b. Oct 6-16 total accumulated rainfall forecast. Image Credit: Eric Snodgrass Northwest Outlook, October 2016 Page 2
Rocky Waters Fisheries A year ago in August 2015, 100% of the state of Washington and Oregon and 50% of Idaho were in D3 stage drought according to the US Drought Monitor. Montana was in better shape, but still had 25% of the state in severe drought. This drought had migrated north from California, but the Pacific Ocean delivered one of the strongest El Niño events since records began in the 1950s. As a result, the winter storm track brought numerous rounds of onshore flow that brought drought busting rains. Fishing grounds north of Alaska in the Arctic have seen an active advance of sea ice after reaching the September ice extent minimum. A few reports have suggested that the advance of the ice this fall has improved fishing in some regions. South of Alaska, very warm sea surface temperatures have held for most of summer and will be a persistent feature in the fall and winter. While the California Current is slightly cooler than average along the Washington and Oregon coast, the Alaska Gyre is quite warm for this time of year. Figure 2a. Arctic sea ice extent. Image Credit: National Snow and Ice Data Center, Boulder, CO Northwest Outlook, October 2016 Page 3
Figure 2b. Sea surface temperature anomalies with inlaid figure of the coastal sea surface temperatures. Image Credit: NOAA (http://www.ospo.noaa.gov/data/sst/contour/washngtn.cf.gif, http://www.esrl.noaa.gov/psd/map/clim/sst.shtml) What About Winter? There are two features to watch in the Pacific Ocean this fall and winter. First is the warm pool of water south of Alaska (Fig 2b.) These warm waters will impact the position and strength of the jet stream. Second, the weak La Niña forming in the Central Pacific is correlated with cooler and wetter winter conditions. This will compete with the warmer ocean temperatures south of Alaska. Here are the impacts for this winter: Expect a very active jet stream. This will create a very active storm track and highly variable weather conditions rather than persistent warm or cool periods. Plan for near-average temperatures this winter as there are no strong signals as of early October to suggest winter will be biased cold or wet for December through February. Long-range forecast guidance suggest slightly wetter than normal conditions for winter. o Low probability of significant drought development. o Low probability of below average snowpack in the mountains. Northwest Outlook, October 2016 Page 4
Figure 3. (Left) Winter forecast graphic. (Top right) NOAA CFSv2 Precipitation Anomaly forecast for Dec. 2016-Feb. 2017. (Bottom right) NOAA CFSv2 Temperature Anomaly forecast for Dec. 2016-Feb. 2017. Image Credit: Eric Snodgrass and NOAA (http://origin.cpc.ncep.noaa.gov/). Northwest Outlook, October 2016 Page 5