#Drought news: A plethora of Pacific storms hit Colorado

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


A plethora of Pacific storms and moisture slammed into California and most of the West, dumping copious amounts of precipitation on the northern two-thirds of the state and Sierra Nevada. This very wet week maintained the great start to the Water Year (since Oct. 1) across the West where NRCS SNOTEL basin average precipitation was above or much above normal at nearly every major basin while basin average snow water content was at or above normal in most Western basins. With more than a foot of precipitation falling on the Sierra Nevada (locally 20.7 inches at Strawberry Valley, CA), most major reservoirs were at or above its Jan. 10 historical average, USGS monitored streams were at near or record high flows, Jan. 10 state snow water content was at 135%, and the Northern Sierra 8-station, San Joaquin 5-station, and Tulare Basin 6-station precipitation indices topped their wettest previous year as of Jan. 10. Accordingly, major drought improvements were made not only to California but at many areas of the West, including parts of Nevada, Utah, Oregon, Idaho, Montana, Wyoming, and Colorado. There were a few areas in southern California, however, that have yet to receive a bountiful Water Year and see any hydrologic improvements, so no changes were made there. Elsewhere, by the time the storms reached the Nation’s mid-section little moisture was available, so most locations observed little or no precipitation during the week. Farther east, an influx of Gulf and Atlantic moisture into the storm systems produced light to moderate precipitation across the eastern third of the U.S., resulting in a few improvements but mainly keeping conditions unchanged. The precipitation included a Jan.6-7 snow storm from Tennessee and northern Georgia northeastward across western North Carolina and eastern Virginia and along the mid-Atlantic and New England Coasts. Much colder air enveloped the lower 48 States as temperatures averaged below normal across most areas. Weekly anomalies of -10 to -25 degF were found across the Northwest and northern High Plains and -5 to -15 degF in the Great Plains and Midwest while seasonable readings were found in the Southwest, Florida, and parts of New England. Improvements were made on the leeward sides of the Hawaiian Islands (except Oahu) thanks to a wet December…

The Plains

Similar to the Midwest, minimal precipitation and subnormal temperatures prevailed across the Plains. In Texas, precipitation was limited to the northern Panhandle (0.2-0.4 inches) along with some small trimming of D0, and in the extreme southeastern coast (0.2-0.6 inches). Meanwhile, short-term dryness and drought expanded in the northeast where it was dry this week. Central Oklahoma saw 0.1-0.3 inches of liquid equivalent precipitation in the form of snow (2-5 inches), but this wasn’t enough to deter additional deterioration as reported impacts from ranchers and farmers indicated ground level conditions were worse than what the indices and products suggested. Reports from former state agriculture officials indicated that 60% of the farm ponds in Woodward, Harper, western Woods and Major, Ellis, and northern Roger Mills counties were dry, and that pastures and winter wheat crops were wiped out. It is possible that major relief from the 5-year 2010-2015 drought was more concentrated from south-central through east-central Oklahoma, and that recent dryness, warmth, and windy conditions have exacerbated the impacts across northern and western Oklahoma. Nevertheless, the combination of short-term (out to 90-days) dryness and worse than expected ground-level impacts prompted an expansion of D2 into north-central Oklahoma, and D1 in southwestern and northern Oklahoma, southeastern Kansas, northwestern Arkansas, and into Missouri (see Midwest Summary). Farther north, light precipitation (0.1-0.3 inches) and frigid air was enough to keep conditions unchanged in the remainder of Kansas, eastern Colorado, Nebraska, and the western Dakotas…

The West

As mentioned in the Summary, major changes were made in many areas of the West due to this week’s parade of moisture-laden Pacific storms and an already wet Water Year (WY), with California the greatest recipient of drought improvements this week. With more than 2 inches of precipitation falling from southwestern Washington southward to Los Angeles, CA, including over a foot along the northern and central California coast and on the Sierra Nevada range, significant increases were made to the capacity of the state’s major reservoirs as most were above the normal Jan. 10 historic levels and still filling with most USGS monitored streams at near or at record high flows. The state’s Sierra snow water content (SWC) was also well above its Jan. 10 normal, with the north (13.5”, or 111%), central (16.9”, or 130%), and south (17.9”, or 171%) producing a state average of 16.2”, or 135%. The Northern Sierra, San Joaquin, and Tulare basin station precipitation indices all exceeded their wettest year (1982-83; 1968-69 for Tulare) as of January 10 with 41.9 (203%), 30.8” (199%), and 20.0 (190%) inches, respectively. In fact, the Northern Sierra index gained 13.2 inches since Jan. 1, or 26% of its ANNUAL average in 10 days. Oroville Reservoir started the New Year with a deficit in its conservation pool of 750,000 acre-feet, but has gained 350,000 acre-feet in the past 2 days. Since northern portions of California also benefited from a decent Water Year last year, 1- to 2-category improvements were made. In contrast, with long-term drought impacts more severe and widespread in southern sections since the 2015-16 WY marked its fifth consecutive year of drought, only a 1-category improvement was made to most areas since above ground (reservoirs) and underground (wells) water supplies still lagged below normal. And in southern Santa Barbara, Ventura, southern Kern, and northwestern Los Angeles counties, D4 remained intact as the WYTD has been below normal while hydrologic impacts lingered. For example, Lake Cachuma (205,000 acre-feet facility) currently has 16,386 acre-feet, including a measly 191 acre-feet gained during the past 2 days. Lakes Casitas and Piru in Ventura County and several reservoirs in Los Angeles County are still well below normal and have not received any recharge. Lastly, even with the rains, no stream flows have been generated in the Santa Ynez, Ventura, and Santa Clara watersheds. Elsewhere in the West, decent snows (0.5-3 inches liquid equivalent) blanketed northwestern Nevada, eastern Oregon, central Idaho, western Montana, southeastern Wyoming, central Colorado, and central Utah, increasing the WYTD basin average precipitation and snow water content to above normal (along with numerous drought indices either normal or wet at various time periods), resulting in a 1-category improvement. Some reservoirs were still below normal in these areas, but the decent snow pack should greatly contribute to a good spring snow melt runoff and recharge if conditions are maintained. In the northern Rockies, however, although the WYTD precipitation has averaged above normal (100-128%), the basin average SWC has averaged below normal (68-91% on Jan. 10). This area will need to be watched for possible D0(S) development if the precipitation and SWC drop below normal during the remainder of the winter. In the Southwest, although precipitation was generally light (0.2-1 inch) or zero (in southeastern California, southern Arizona, and southern New Mexico), wet weather the previous 2 weeks with some improvements warranted status quo this week. Similar to the northern Rockies, southern New Mexico will need to be watched for D0 development as the Jan. 10 SWC is well below normal (15-49%) while the WYTD precipitation is near or above normal (92-116%)…

Looking Ahead

During the next 5 days (January 12-16), heavy precipitation is expected to shift away from California to the south-central Plains (where recent conditions have steadily worsened) as the 5-day QPF from WPC predicts 3-5 inches of precipitation over central Oklahoma. Welcome precipitation (1-3 inches) is also forecast for northern and central Texas, western Oklahoma, most of Kansas and Missouri, the Ohio Valley, and eastern Great Lakes region. Light precipitation should linger over the southwestern quarter of the Nation (including California) and in the Northeast. Little or no precipitation should occur across the northern sections of the Rockies and Plains, and in the Southeast. Subnormal temperatures are expected in the West and central Plains while above-normal readings occur in the southern Plains and eastern half of the Nation.

During January 17-21, the odds are tilted toward above median precipitation in the West and eastern half of the U.S., with sub-median precipitation favored in the southern Plains and western Alaska. Much of the lower 48 States should see above-normal temperatures, especially the eastern half, while subnormal readings are strongly favored in Alaska.

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