October in the West
Well above normal precipitation was observed across a large area of the West this month, extending from central California northeast to eastern Montana. Many October precipitation records were set between northern California and the Canadian border. In contrast, much of the Southwest observed drier than normal conditions. October temperatures were generally near to slightly below normal in the coastal states, transitioning to significantly above normal in the Southwest, most notably in the Four Corners states.
Several storm systems impacted the Northwest this month, bringing widespread above normal precipitation to the region. The most notable system occurred October 14-17, when two atmospheric rivers made landfall in succession. Some locations on Washington’s Olympic Peninsula and the Klamath Mountains spanning the California-Oregon border received over 15 in (400 mm) of precipitation from the event and high elevation stations in the Sierra Nevada reported over 12 in (30 cm) of snow. Records for wettest October were set across the state of Washington, with Seattle recording 10.05 in (255 mm); Yakima 2.43 in (62 mm); and Spokane 6.23 in (158 mm). Records for Seattle began in 1945, Yakima in 1946, and Spokane in 1881. Elsewhere in the Northwest, many locations also saw top-10 wettest Octobers. Lewistown, Montana logged its wettest October in a 121-year record with a total 4.01 in (102 mm) precipitation, 355% of normal. Portland, Oregon, reported 8.31 in (211 mm), its 2nd wettest October since records began in 1938. Eureka, California also reported its second wettest October on record, receiving 10.92 in (277 mm), 488% of normal. Records for Eureka began in 1886. This month’s storms were favorable for precipitation to spill over major mountain barriers. In the lee of the Sierra Nevada, Reno observed 2.43 in (62 mm) precipitation, 476% of normal and the 2nd wettest October since records began in 1937. October’s abundant precipitation allowed for significant improvement of drought conditions across the Northwest, leaving Washington, western Oregon, far northwestern California, and nearly all of Idaho and Montana free of any drought class designation in the US Drought Monitor.
Precipitation was limited across the Southwest this month, with most locations receiving less than 75% of their October normal. Tucson, Arizona, reported 0.11 in (3 mm), 11% of normal and the 20th driest October since records began in 1946. In northeastern New Mexico, Clayton logged 0.03 in (1 mm), 3% of normal and tie for 14th driest in a 121-year record. Across the border in southern Colorado, Colorado Springs reported no measurable precipitation to tie with 1934 for the driest October since records began in 1894. Normal October precipitation for Colorado Springs is 0.82 in (21 mm).
Temperatures were near to slightly below normal across the Northwest, owing to periods of storm activity moderating temperatures. In contrast, well above normal temperatures dominated across the Southwest resulting in many all-time warmest October records. Tucson, Arizona (77.5 F/25.3 C, 6.5 F/3.6 C above normal), and Clayton, New Mexico (62.0 F/16.7 C, 7.2 F/4 C above normal), both reported their warmest Octobers on record. Records for Tucson began in 1946 and Clayton in 1896. Phoenix, Arizona, observed its latest day >=100 F (37.8 C) on record October 27, beating the previous record of October 23 set in 2003. The combination of warm and dry weather across the Southwest this month allowed for expansion of abnormally dry conditions across Colorado and northeastern New Mexico. Severe to exceptional drought remained entrenched in central and southern California as well as western Nevada this month, and moderate drought conditions persists in northern Utah and large portions of Arizona.
Most of Alaska was drier than normal this month, and several locations in southeast Alaska experienced their driest October on record. Juneau observed only 2.59 in (66 mm) precipitation, 30% of normal and the driest October since records began in 1936. Temperatures were above normal in all but the southeastern part of the state, with several locations shattering previous October records. Barrow reported an average temperature of 30.1 F (-1 C) for the month, 12.9 F (7.2 C) above normal. This was 2.4 F (1.3 C) higher than the previous record of 27.7 F (-2.4 C) set in 1911. Records for Barrow began in 1901. Further south, most of Hawaii observed below normal precipitation, with the exception of some Big Island locations. Honolulu, Oahu, recorded 0.12 in (3 mm) for the month, 6% of normal and the 6th driest October since records began in 1940.
Significant Events for October 2016
October 14: Tornado outbreak along Oregon Coast: Many locations in the Pacific Northwest experienced wind gusts in excess of 80 mph (36 m/s) ahead of a potent storm system. A rare tornado outbreak occurred along coastal Oregon. One tornado, an EF2 near Manzanita, Oregon, damaged over 100 structures.
October 14: Windstorm helps to ignite, spread several fires in Reno, Nevada, area: Winds gusts exceeding 75 mph (34 m/s) were associated with several rapidly spreading fires. The most destructive was the Little Valley Fire, which burned 2300 acres (930 hectares) and destroyed 23 homes.