Drought news: Snowy Christmas week in the central Rockies

Click on a thumbnail graphic for a gallery of drought data.

Click here to go to the US Drought Monitor website. Here’s an excerpt:

Summary

Significant precipitation shifted into the Northwest, ending California’s period of favorably wet weather. During the 7-day monitoring period, precipitation totaled 4 inches or more in parts of the Pacific Northwest and ranged from 2 to 4 inches across portions of the northern Rockies. Lingering showers dotted northern and central California, but mostly dry weather prevailed in southern California and the Desert Southwest. Farther east, several disturbances crossing the Plains provided snow in advance of the strongest push of cold air in nearly a month. Snow was also reported as far south as Oklahoma and northern Texas, while generally light freezes were noted in California’s Central Valley. In late December, unusual warmth across the eastern half of the U.S. was replaced by cooler weather. Prior to the push of colder air, near- or above-normal temperatures had dominated the country for 3 weeks. Elsewhere, heavy rain soaked the Southeastern and Atlantic Coast States. The rain largely eased concerns about short-term dryness and drought development, but also caused local flooding. Rainfall was especially heavy, totaling 4 inches or more, from the central Gulf Coast into parts of the Carolinas. On December 23-24, a late-year tornado outbreak accompanied the heavy rain.

As the drought-monitoring period came to an end, a developing storm brought the promise of accumulating snowfall across the southwestern U.S. Any drought-related impacts will be covered next week, since nearly all of the precipitation associated with the storm fell after the cutoff time of 7 am EST (4 am PST) on December 30…

Central and Southern Plains

Rapidly changing conditions in late December—markedly cold weather, along with some light snow and freezing rain—followed a period of relative tranquility. By December 27, daily-record snowfall amounts included 3.5 inches in Oklahoma City, Oklahoma, and 2.0 inches in Wichita Falls, Texas. Additional freezing and frozen precipitation arrived on December 29-30. Nevertheless, there were some small-scale changes (for the worse) introduced across the southern Plains, mostly related to an evaluation of long-term impacts of the multi-year drought on water supplies. For example, reservoirs in Texas were five-eighths (62.6 percent) full at the end of 2014, compared to 64.3 percent at the end of 2013. Historically, reservoirs in Texas are collectively about 80 percent full in late December…

Northern Plains and Upper Midwest

No changes were made across the northern Plains and upper Midwest, where the coldest weather in a month arrived in late December. Several periods of light precipitation preceded and accompanied the return to cold weather. Outside of area of abnormal dryness (D0), Sioux City, Iowa, received enough precipitation during the monitoring period to secure its wettest year on record. Through December 29, the total of 41.36 inches (149 percent of normal) in Sioux City surpassed its 1903 annual standard of 41.10 inches. Farther north, the Red River Valley and neighboring areas remained rather dry at time periods of 30 to 90 days or more, maintaining status quo for the broad area of D0 and the small area of D1…

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.

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