December 30, 2014 - The West, Including California
With the storm track shifting farther north, significant precipitation overspread the Northwest. December 25 became the snowiest Christmas Day on record in Wyoming locations such as Lander (9.6 inches) and Cheyenne (6.8 inches). With precipitation spilling across the High Plains, December 25-26 snowfall totals included 10.6 inches in Scottsbluff, Nebraska; 7.7 inches in Cheyenne, Wyoming; and 5.1 inches in Denver, Colorado. Across the western slopes of the northern Rockies, precipitation was heavy enough to result in some very slight trimming of dryness and drought. Closer to the Pacific Coast, and especially in the Cascades, an interesting winter continued to unfold. Since October 1, season-to-date precipitation in the Cascades has generally averaged 105 to 125 percent of normal. However, with an unusual amount of the precipitation falling as rain, the late-December snowpack contained only about one-third to one-half of its typical amount of water for this time of year—except closer to 75 percent of normal in the northern Cascades of Washington State. This discrepancy—overall wet conditions but meager snowpack—has led to some mixed drought indicators, such as favorable rangeland, pasture, and winter grain growth and improved soil moisture, while concerns persist with respect to the possibility of limited runoff into streams and reservoirs during the upcoming spring snow-melt season.Many of the same concerns persisted in California, especially given the return of drier weather during the last one-third of December. According to the California Department of Water Resources, the high-elevation Sierra Nevada snowpack held only about one-half of its normal water (roughly 5 vs. the normal of 10 inches) for this time of year. At the same time, California’s December rainfall left winter wheat rated 80 percent in good to excellent condition on December 28, according to the U.S. Department of Agriculture. However, California’s rangeland and pastures still have a long recovery ahead of them; they were rated 70 percent poor to fair by USDA on December 28, up only slightly from 65 percent on November 23. Due to heavy rain in extreme northwestern California (and adjacent areas in southwestern Oregon), there was some slight trimming of drought coverage.
Looking Ahead
For the upcoming 5-day period (December 31, 2014 – January 4, 2015), a developing storm will produce an expanding area of precipitation across the southern U.S. On New Year’s Eve, snow will engulf the mountains of the Southwest. Some of the heaviest snow will fall in northern Arizona, although snow levels dropping below 2,000 feet could result in accumulations in some desert locations. Meanwhile, freezing rain may cause holiday travel disruptions in parts of western and central Texas. Later, the storm will shift eastward, bringing a return of heavy rain (1 to 3 inches) to the South and East. Some sleet and freezing rain may occur along the northern edge of the precipitation shield. Cold air will remain entrenched nearly nationwide, particularly across the western and central U.S., with freeze-protection measures required for sensitive crops, such as citrus, in parts of California.The NWS 6- to 10-day outlook for January 5 – 9, 2015, calls for the likelihood of above-normal precipitation in southern Texas and from the Pacific Northwest to the Great Lakes region. Meanwhile, drier-than-normal conditions can be expected in much of the Southeast and from central and southern California eastward to the southern Plains. Cold conditions will persist from the Midwest into the Northeast, but warmer-than-normal weather will continue across southern Florida and return across much of the West.
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)
