February in the West
January’s cool and dry conditions continued throughout February for much of the West. The position of the high pressure ridge typically present over the West in February was shifted slightly west of its climatological mean, allowing cold air masses to dip southward east of the Sierra and ample precipitation to reach the Rockies. The inland Northwest was the only area to see above normal temperatures this month, the fourth consecutive month this area has been warmer than average.
February was a dry month, especially in the Cascades/Sierra Nevada, with small average or moist pockets in the central Great Basin and northern and central Rockies. This followed on the heels of a very dry January as well. After a wet start to winter in December, many California and western Nevada locations saw January-February precipitation totals in the 10 driest on record. Downtown San Francisco recorded only 1.82 in (46 mm) thus far in 2013, the 5th driest January-February in a 163-year record. Nearby Santa Cruz, CA recorded its driest such period since 1893 with 1.22 in (31 mm; normal is 12.52 in / 318 mm). Further north, Ukiah and Eureka, California, saw their 2nd and 3rd driest January-February, respectively. A grand total of 0.12 in (3 mm) liquid precipitation fell at the Reno, Nevada, airport during January and February, the driest such period since the record began in 1937. Sierra snowpack water equivalent fell to 60-70% of normal at month’s end. Further south, Los Angeles, California, experienced its 15th driest January-February in a 69-year record at 1.5 in (38 mm), 25% of normal.
The position of the high-pressure ridge this month helped guide storm systems into the eastern Great Basin and Rockies. Despite above normal February snowfall, snow water equivalent for river basins of northeastern Nevada stood at 80-95% of normal at the end of the month. Further east, Salt lake City, Utah, enjoyed its 16th snowiest winter-to-date, but 22nd driest February on a 139-year record. Colorado Springs, Colorado recorded the 9th wettest February on record with 0.9 in (23 mm) precipitation and 13th snowiest at 10.6 in (27 cm). This month was also the first since September 2012 that Pueblo, Colorado recorded above normal precipitation. February precipitation helped to ease persistent drought conditions in western Wyoming and Colorado, while much of the eastern portions of these states remained categorized as severe to exceptional drought by the U.S. Drought Monitor. Even with this month’s snowfall, snow water equivalent for Colorado basins stood at 65-80% of normal at the end of the month. Snowpack in Wyoming’s basins fared slightly better, between 75% and 100% of normal. Most basins in Washington, Oregon, Montana, and Idaho reported above normal snow water equivalent at the end of February.
While most of the West was cooler than normal, Montana logged its third consecutive month of above normal average statewide temperatures at 28.2 F (-2.1 C), 3.9 F (2.2 C) above normal. Eleven of the past 13 months have been warmer than average for the state. Unusually cold temperatures continued in the Great Basin. Ely and Winnemucca, in northeastern Nevada, recorded their 13th coldest winters on record at an average 22.6 F (-5.2 C) and 26 F (-3.3 C), respectively. Records began in 1893 at Ely and 1877 at Winnemucca. Temperatures more than 10 F (5.5 C) below normal were also seen in northwestern Utah in the Great Salt Lake Desert.
Strong northeast trade winds and heavy precipitation arrived on the windward sides of the Hawaiian Islands this month, helping to alleviate persistent drought in these areas. Hilo, Hawaii recorded 23.12 in (587 mm) for the month, 242% of normal and the 7th wettest February since records began at Hilo in 1949. After having above normal January precipitation, leeward locales such as Honolulu and Lihue returned to the past year’s trend of below normal precipitation.
Following a warmer than normal January statewide, mild temperatures dominated the Interior and southern regions of Alaska, while the Northern and Western regions were a chilly 6-8 F (3-4 C) below the February normal. Persistent precipitation fell in the southern portion of the state, especially the Southeast. January’s wet conditions continued in Juneau, which recorded 6.61 in (167 mm) for the month, the 7th wettest February on its 64-year record.
Significant Events for February 2013
February 21: High stream flow in Kauai’s Na Pali coast: Heavy rainfall over the island of Kauai lead to above normal flow in Hanakapiai Stream on the Na Pali coast. Over 50 hikers were trapped overnight as they could not ford the swollen Hanakapiai stream and high winds prevented rescue efforts.
February (all month): Inversions and poor air quality in Salt Lake City: The frigid temperatures and strong inversions observed in January were fewer and weaker this month though still observed. In Salt Lake City, 22 days this winter exceeded federal air quality standards for pollution levels, as compared to a single day last winter.