November in the West
While most of the conterminous United States remained drier than normal this month, several systems delivered above average precipitation to portions of the Northwest. Over the last few days of November, a series of atmospheric rivers, narrow filaments of high water vapor transport with subtropical origins, brought heavy precipitation to northern and central California as well as parts of Oregon and Idaho. Throughout the West, average monthly temperatures remained above normal with many locations reporting a positive anomaly of at least 3.0 F (1.6 C).
Dry and warm conditions prevailed for much of the Southwest this month. Phoenix, Arizona saw its second warmest November on record at an average 68.4 F (20.2 C). Records at Phoenix began in 1895. In Colorado, Denver airport received only 1.7 in (43 mm) of snowfall this month, 20% of its normal 8.7 in (223 mm). In the Great Basin, Las Vegas, Nevada recorded its 3rd warmest November at 60.1 F (15.6 C) in a record dating back to 1937 and Ely, Nevada logged its 4th warmest November at 39.8 F (4.3 C), 6.1 F (3.4 C) above normal. Tonopah, Nevada tied 1995 for warmest autumn on record with a September-October-November average of 56.0 F (13.3 C). Records in Tonopah began in 1902. Throughout New Mexico, year-to-date average temperatures have been some of the highest on record. The January-November average temperature in Albuquerque was 62.0 F (16.7 C), the warmest such period in a record beginning in 1914. Roswell and Clayton also saw near-record year to date average temperatures. In addition, Clayton experienced its driest January-November period, receiving only 7.4 in (188 mm) so far this year and no precipitation this month. Normal January-November precipitation at Clayton is 15.43 in (392 mm) and records began in 1896.
The Northwest was dominated by wet and warm conditions. Between November 28-30, 3-day precipitation totals farther south at windward locations in California’s Coast Range between Big Sur and the San Francisco Bay Area were over 6 in (152 mm). This event brought monthly totals to over 200% of normal at some locations. Farther inland, some of the highest 3-day totals in the southern Cascades and northern Sierra Nevada were over 8 in (203 mm). Several long-standing daily precipitation records were surpassed in northern California and Oregon. Mt. Shasta City, California received 3.89 in (99 mm) on November 29, shattering the previous record of 1.81 in (46 mm) set in 1932. Medford, Oregon received 2.22 in (56 mm) on the 29th, breaking the daily record of 1.25 in (32 mm) set in 1917. Some of the highest daily totals were 5.1 in (130 mm) on the 30th at Big Sur, and 5.41 in (137 mm) at the Mt. Shasta RAWS on the 29th. Further north, Seattle, Washington recorded its 4th wettest November on record with a total of 9.17 in (233 mm) and also its 9th warmest at an average 47.4 F (8.6 C) for the month. Several other western Washington locations also recorded top 10 warmest November temperatures. Above normal monthly precipitation totals were also observed throughout Montana, providing relief from persistent dry conditions this year. For the year-to-date, 2012 was the warmest on record at Billings with an average 53.3 F (11.8 C) and also the driest at a total 6.86 in (174 mm). Records at Billings began in 1934. Miles City, Montana and Sheridan, Wyoming also experienced top 10 warmest and driest conditions year-to-date on record.
Dry conditions persisted in Hawaii. Following its driest October in a record beginning in 1950, Lihue, Kauai received only 0.58 in (14.7 mm) this month and tied 1968 for the driest November on record. Stations throughout the state recorded below normal precipitation, with percentages of normal as low as 9% in Honolulu. At the end of November, the entirety of the state was experiencing some level of drought.
Significant Events for November 2012
November 18-19: Western Oregon and Washington high winds: The passing of a cold front brought high winds to western Oregon and Washington. Some of the highest wind gust speeds were recorded in southwestern Washington on the morning of the 19th. Naselle Ridge recorded 114 mph (184 kph) and at Megler Tower winds gusted to 101 mph (163 kph). At the Columbia River Bar, 97 mph (156 kph) was recorded. The high winds downed trees and power lines and caused one fatality.
November 29-30: High winds in San Francisco Bay Area: Another passing cold front brought strong winds to the Bay Area. Wind speeds reached 84 mph (135 kph) in Los Gatos, California and 76 mph (122 kph) in San Jose, California. San Francisco airport recorded winds near 50 mph (80 kph). High winds were also recorded in the along the Sierra crest and foothills and along the eastern Sierra and western Nevada.
November 18-27: Dense radiation fog in California’s Central Valley: After precipitation on the 15-18th saturated the soil, clear skies and light winds created excellent conditions for the development of radiation fog in the Central Valley. On the morning of November 27th, dense fog near Chowchilla, California brought visibility down to 300 ft (91 m). A multi-car accident with 3 fatalities occurred in the heavy fog conditions.