#Drought news: Warmer than average temperatures lead to expansion of D1 (Moderate Drought) in E. #Colorado

Click on a thumbnail graphic to view a gallery of drought data from the US Drought Monitor.

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

This Week’s Drought Summary

A low pressure system propagated eastward across much of the southern tier states early in the period (March 4-6) and merged with a short-wave trough dropping southeastward from the Midwest before moving off the Mid-Atlantic coast on March 7. This system dropped more than 2 inches of rainfall over large areas from extreme southeastern New Mexico eastward to South Carolina. Some areas of central Alabama and Georgia saw more than 5 inches of rainfall, which fell over saturated soil. However, much of the heavier rainfall remained north of the I-10 corridor from southern Texas to northern Florida, while areas south of I-10 received only modest amounts, which were not nearly enough to reduce deficits. The Pacific Northwest and California also saw some precipitation over the past week, but amounts were not enough to reduce any deficits. Some recent dryness over southern Iowa and northern Missouri was mitigated a bit with near- to above-normal precipitation falling last week as well. Deficits increased in the Mid-Atlantic and New England over the past 30 days, but were kept at bay, as these areas saw 0.1 to 1 inch and 0.1 to 0.5 inches of rainfall, respectively. The active storm track continued last week for Alaska, with the southeastern Panhandle receiving 2 to 6 inches of precipitation over many areas. This precipitation, along with near- to below-normal temperatures, has finally produced above-normal snowpack in the Alaska Panhandle for the first time in 7 to 8 years, warranting D0 removal. Hawaii remained dry on the leeward slopes last week due to persistent trade winds, leading to some D0 expansion and development on the Big Island and Oahu, respectively. Puerto Rico saw D0 removal, as northern portions of the island saw much above-normal precipitation, eliminating short-term deficits…

High Plains
D1 was expanded a bit in northeastern Colorado (i.e. existing D1 areas were connected). This area has continued to experience warmer-than-average temperatures in recent weeks, which has had adverse effects on winter wheat and rangelands prior to green-up. In addition to SPIs showing D1 (and worse over longer periods at a couple locations), USGS stream flows in surrounding locations were showing flows below the 10th percentile. Some drier-than-normal conditions crept into eastern portions of the Dakotas over the past 30 days (25 to 50 percent of normal precipitation, with some small areas of 10 to 25 percent of normal in extreme eastern South Dakota). However, 60- and 90-day precipitation was near and above normal, respectively, for these areas. Therefore, it was status quo for the rest of the High Plains Region…

D0 was expanded to the coast in Monterey County, California, with 5 to 10 inch year-to-date (YTD) deficits over much of the county (greater than 10 inch deficits on some of the windward slopes). D0 was also expanded eastward and southeastward from Los Angeles County in favor of those areas receiving 10 to 25 percent of YTD precipitation with some locations seeing 25 to 50 percent of normal water-year-to-date (WYTD) precipitation. However, this area was not extended further southward as most of San Diego County has seen near-normal precipitation going back 6 months, and near-normal rainfall over the past week. D1 was expanded to connect the areas in California and Nevada (near Reno, Nevada). March 10 snow water content (SWC) was still below normal, and YTD precipitation was 5 to 10 percent of normal within the expanded area. D1 was also expanded southward into San Luis Obispo, Santa Barbara, Ventura, and Los Angeles Counties in California, with several locations seeing the January-February period falling within the top 5 driest on record. This has already had large impacts to natural vegetation needed for feeding livestock, as many ranchers have resorted to supplemental feeding. Similar reports have come from northern California (Siskiyou County), over the past couple of weeks, along with unregulated streams running dry, hence the D1 expansion there as well.

Elsewhere in the Western Region, D0 was reduced in southeastern New Mexico and D1 was removed in eastern New Mexico due to last week’s rainfall. In addition, many of these areas are seeing greater than 150 percent of normal YTD precipitation and near-normal (former D0 and D1 areas) and above-normal (former D0 area) WYTD precipitation. D0 was also expanded in eastern Nevada (northeast White Pine County). 6-month precipitation is 25 to 50 percent of normal, which has become worse over the past 30 days (areas of 2 to 5 percent of normal), supporting ground reports of abnormal dryness. D1 was expanded eastward in central and northern Washington. Although the past 60 to 90 days have seen near-normal precipitation for these areas, 6-month deficits show precipitation at 25 to 50 percent of normal and little to no precipitation has fallen in the past 30 days, which has contributed to some below-normal snowpack over eastern portions of the state. D1 was also expanded westward in northwest Oregon (northern Willamette Valley) and eastward in southeastern Oregon in favor of WYTD deficits of over 13 inches and below-normal SWC. In addition, 7-day USGS stream flows continued to be below the 10th percentile last week. Additional D1 expansion was made in southeastern Oregon due to 25 to 50 percent of normal YTD and WYTD precipitation…

D0 was expanded northward from the Gulf Coast of Louisiana, Mississippi, and Alabama. Many of these areas have 6-month deficits of over 8 inches; 6-month deficits over 12 inches in southeastern LA (i.e. 50 to 75 percent of normal). Rainfall over the past 30 days has been particularly low, with precipitation falling to 25 to 50 percent of normal, with some locations in the new D1 area seeing 10 to 25 percent of normal. Some expansion of D1 was made northeast of Corpus Christi, Texas, and D2 toward the coast, as USGS stream flows were well below normal at many locations and soil moisture has diminished further in recent weeks. Meanwhile, many areas in western and northern Texas (north of the I-10 corridor) saw anywhere from 0.5 to 3 inches (in isolated locations). The heavier rainfall extended southward into the upper Rio Grande Valley where many areas saw 0.25 to 1 inch of rainfall, warranted some reduction in D0, D1, and D2 areas along the river. It is status quo elsewhere for the Southern Region, including southwestern Oklahoma, whose 7-day totals (0.25 to 1 inch) were not enough to cut into rainfall deficits…

Looking Ahead
During the next 5 days (March 12-16), low pressure will be moving into southern California and the Southwest. This will help to deepen troughing over the western CONUS allowing for a southern stream of moisture to develop, enhancing chances for precipitation over California, the Southwest, southern Great Plains, and the Ohio River Valley. Below-normal temperatures (5°F to 10°F) are also expected for much of the West Coast and northern Rockies. Meanwhile, the Gulf Coast is likely to see temperatures 5°F to 10°F above normal, south of a lingering frontal boundary.

The 6-10 day (March 17-21) extended range forecast favors an amplified 500-hPa height pattern with Pacific ridging building northward into Alaska, leading to above-normal temperatures and precipitation over much of Mainland Alaska, with near- and below- normal precipitation along the southern coast and southeastern Panhandle. Troughing is favored over much of the western CONUS, enhancing probabilities for below-normal temperatures and above-normal precipitation in central and southern California and the southern Rockies, which would be welcome for areas with below-normal snowpack. Above-normal precipitation is favored for the eastern two-thirds of the CONUS, as the pattern is favorable for lee-side cyclogenesis east of the Rockies. Weakly above-normal chances for precipitation are favored along the Gulf Coast east of Texas, with below-normal probabilities favored over the drier areas of the Florida Peninsula. The odds favor above-normal temperatures in the eastern half of the lower 48 states.

US Drought Monitor one week change map ending March 10, 2020.

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