Western Regional Climate Center

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October in the West

October 2013

Cooler than normal temperatures dominated the West this month for the first time since the beginning of the year. The southwestern portion of the region had warm days and very cool nights, whereas the northeastern portion of the region had very cool days and warm nights. Several low pressure systems swept cold air into the region, and clear skies and low humidity between systems allowed for enhanced nighttime cooling. Precipitation was below normal for a majority of the West, though southeastern Montana and Wyoming saw near record rain and snow. Many locations throughout the West saw their first measurable snowfall of the season.

After a record wet September in the Northwest, many locations saw one of their 10 driest Octobers. Spokane, Washington received 0.09 in (2 mm) rainfall, 1.09 in (28 mm) below normal, the 5th driest October in a 125-year record. Missoula, Montana recorded its third driest October in a 121-year record at 0.06 in (2 mm), 7% of normal. Eugene, Oregon received 0.58 in (15 mm), the 5th driest October since records began in 1939. Dry conditions returned to northern California, where Eureka rainfall totaled 0.05 in (1 mm), 2% of normal, the 2nd driest October in a 121-year record. Downtown San Francisco received no measurable October precipitation for the 5th time in the past 100 years. Dry conditions persisted in southern California, where many locations received less than 10% of normal rainfall. Downtown Los Angeles logged 0.06 in (2 mm), a scant 9% of normal. Elsewhere in the Southwest, Phoenix, Arizona received only trace precipitation and Albuquerque, New Mexico recorded 16% of its normal October precipitation.

In contrast, locations throughout Wyoming saw one of their top-ten wettest Octobers. This was extremely beneficial for a state that has been experiencing severe, persistent drought. By the end of the month, the area of the state with drought designations in the US Drought Monitor had been reduced by 20%. Casper, in central Wyoming, received 3.03 in (77 mm) of precipitation, 272% of normal, the location’s 3rd wettest October in a 75-year record. It was also the 4th snowiest October in Casper with 16.4 in (42 cm) of snow measured for the month. Lander, Wyoming saw its 5th wettest October at 3.08 in (78 mm), 239% of normal. Southeastern Montana also received impressive precipitation. Billings logged its 5th wettest October in an 80 year record with 2.57 in (65 mm). Several locations in the lee of the Sierra also received above normal precipitation. Winnemucca, in northern Nevada, had its 3rd snowiest October since records began in 1877 at 6.6 in (17 cm). Precipitation at Winnemucca totaled 1.48 in (38 mm), 220% of normal. Throughout mountainous areas of the West, snow water equivalent was generally above normal due to early season snowfall, though many of these areas saw below normal precipitation totals for the month.

October temperatures averaged moderately to much cooler than normal throughout the West, with several long-record stations observing one of their 10 coolest Octobers. Kalispell and Butte, Montana both logged their 5th coolest Octobers at an average 39.2 F (4.0 C) and 36.7 F (2.6 C), respectively. Records began in Kalispell in 1899 and in Butte in 1894. Lander, Wyoming recorded an average 40.5 F (4.7 C) for the month, 5 F (2.8 C) below normal and the 6th coolest October since records began in 1948. Winnemucca, Nevada observed its 7th coldest October in a 137-year record at an average 49.3 F (9.6 C). In eastern Oregon, John Day recorded its coldest October since consistent records began in 1953 at 43.3 F (6.3 C), or 5 F (2.8 C) below normal. Winslow, Arizona recorded an average 52.5 F (11.4 C) for October, the 6th coolest since records began in 1898. Winslow, Kalispell, and Winnemucca last saw below normal October averages in 2009; Butte, Lander, and John Day all noted below normal October averages in 2012 as well.

While cool temperatures dominated the contiguous western US, a persistent ridge over Alaska brought record high temperatures to the state. Above normal temperatures were recorded throughout the state, with the greatest anomalies in the Interior region. Temperatures at Anchorage averaged 44.2 F (6.8 C) for the month, 9.4 F (5.2 C) above normal and the warmest October on record. In McGrath, average temperature was 13.5 F (7.5 C) above normal at 38.7 F (3.7 C), the warmest since records stared in 1941. The average temperature in Fairbanks was 36.1 F (2.3 C), 11.9 F (6.6 C) above normal and the third warmest since records began in 1930. Precipitation was abundant in southern Alaska this month, with Valdez recording 17.83 in (453 mm), 216% of normal and the wettest October on record. Hawaii saw a much drier October, with a majority of stations reporting <50% of normal rainfall. Molokai Airport recorded 0.17 in (4 mm), 9% of normal and the 5th driest October in a 65-year record. On Oahu, Kaneohe reported only trace precipitation, 2.98 in (76 mm) below normal. Kauai fared better than the other islands, with Lihue receiving 7.99 in (203 mm), 209% of normal. Lihue had not seen above normal October rainfall since 2004.

Significant Events for October 2013

October 3-5: Wyoming/SE Montana Blizzard: Storm snowfall totals at higher elevation locations were around 30 in (76 cm). Heavy snow snapped tree limbs and knocked out power lines. Travel was impacted in eastern Wyoming due to highway closures. The blizzard impacts were much more severe over the state line in South Dakota.

October (all month): Warm temperatures in Alaska: Warm late autumn temperatures delayed the freeze-up of lakes and rivers in Alaska’s Interior. These bodies of water are typically beginning to freeze by late October.

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