January 6, 2015 - The West, Including California
Aside from a few small improvements in Arizona, the Southwestern storm of late-December 2014 and early-January 2015 did not provide enough moisture to dent long-term drought. Nevertheless, the storm produced some unusual weather in the Desert Southwest, including some rare snow. In Needles, California, where 0.3 inch fell on December 31, snow had not fallen since February 2, 1985. Needles had never before received measurable snow in December, and had not seen a greater amount since January 25, 1949, when 2.0 inches fell. Similarly, an inch of snow fell on New Year’s Eve in Bullhead City, Arizona, marking the first accumulation in that area since January 11, 1949. Laughlin, Nevada, and Lake Havasu City, Arizona, both reported a trace of snow on December 31 and January 1; snow had not been observed in Laughlin since February 26, 1987, or in Lake Havasu City since January 24-25, 1949. Meanwhile, Flagstaff, Arizona, reported a 17.3-inch snowfall on December 31 – January 1. Looking at the drought from a longer-term perspective, statewide reservoir levels remained very low in New Mexico and somewhat low in Arizona. Based on preliminary information, New Mexico’s storage on December 31 was 53% of average, compared to 51% a year ago. In Arizona, statewide storage stood at 73% of average at the end of the year, down from 85% on December 31, 2013.Farther north and west, the drought situation remained largely unchanged, although enough precipitation fell across the western slopes of the northern Rockies to further trim abnormal dryness (D0) and moderate drought (D1). In north-central Washington, east of the Cascades, an end-of-year assessment led to a small reduction in the coverage of moderate to severe drought (D1 to D2). End-of-year reservoir reports have begun to trickle in and indicate the statewide storage was higher on December 31, 2014, than a year ago in Wyoming (124% of average vs. 92%), Montana (112 vs. 104%), Idaho (106 vs 84%), Colorado (103 vs 88%), Washington (99 vs. 76%), Utah (98 vs. 91%), and Oregon (79 vs. 68%). Nevertheless, one concern facing the Northwest—especially in the Cascades and coastal ranges—is the lack of snowpack due to periods of warmth and the large number of “warm” storms. In early-January 2015, the basin-average water content of the snowpack was mostly less than half of normal for this time of year from the Cascades westward, despite above-normal precipitation since October 1, 2014.
The drought depiction in California and Nevada was not changed. Nevada’s reservoir storage remained extremely low—only 21% of average at the end of 2014, compared to 30% on December 31, 2013. (California’s end-of-year reservoir information has not yet been published.) By January 6, the average water content of the high-elevation Sierra Nevada snowpack averaged just 5 inches—43% of normal for this time of year. According to the California Department of Water Resources, the water content of the Sierra Nevada snowpack in an average year typically approaches 30 inches by April 1. In other words, the current Sierra Nevada snowpack contains only 17% of the water typically available when the melt season begins in the spring. Closer to the northern Pacific Coast, water systems that are not dependent on Sierra Nevada runoff are faring better than inland basins. For example, storage in Marin County’s seven reservoirs was 99.9% of capacity on January 4, 2015—well above last year’s 56.0% and the average of 74.8%—following runoff from heavy, late-autumn rainfall. However, average, end-of-year storage in Marin County only represents a tiny fraction (less than three-tenths of 1%) of California’s total average reservoir holdings. In addition, ongoing impacts of the 3½-year drought along California’s northern coast—and elsewhere in the state—include low groundwater reserves and stress on native vegetation and perennial crops such as orchards and vineyards.
Looking Ahead
For the upcoming 5-day period (January 8-12), very cold weather will continue to dominate the central and eastern U.S. During the cold snap, snow showers and squalls will rage downwind of the Great Lakes. In contrast, mild, dry weather will prevail in much of the West. During the weekend, rain will develop in the western Gulf Coast region. As precipitation spreads northeastward early next week, the interaction between moisture and lingering cold air could result in snow, sleet, and freezing rain across parts of the South, East, and lower Midwest.The NWS 6- to 10-day outlook for January 13-17 calls for the likelihood of below-normal temperatures in most areas east of a line from Texas to Wisconsin, while warmer-than-normal weather can be expected across the northern High Plains and the West. Meanwhile, below-normal precipitation will be the probable outcome across the northern half of the nation, as well as southern California and environs, but wetter-than-normal conditions will likely prevail in the southern Atlantic States and southern portions of the Rockies and High Plains.
Author(s):
Brad Rippey, U.S. Department of Agriculture
Dryness Categories
D0 ... Abnormally Dry ... used for areas showing dryness but not yet in drought, or for areas recovering from drought.Drought Intensity Categories
D1 ... Moderate DroughtD2 ... Severe Drought
D3 ... Extreme Drought
D4 ... Exceptional Drought
Drought or Dryness Types
S ... Short-Term, typically <6 months (e.g. agricultural, grasslands)L ... Long-Term, typically >6 months (e.g. hydrology, ecology)
