National Drought Summary February 28, 2017 The discussion in the Looking Ahead section is a description of what the official national guidance from the National Weather Service (NWS) National Centers for Environmental Prediction is depicting for current areas of dryness and drought. The utilized NWS forecast products include the WPC 5-day QPF and 5-day Mean Temperature progs, the 6 10 Day Outlooks of Temperature and Precipitation Probability, and the 8 14 Day Outlooks of Temperature and Precipitation Probability valid as of late Wednesday afternoon of the USDM release week. The NWS forecast Web page used for this section is http://www.cpc.ncep.noaa. gov/products/forecasts/. Several weather systems traversed the contiguous U.S. (CONUS) in the fast-moving upper-level flow during this U.S. Drought Monitor (USDM) week. Upper-level troughs, surface fronts, and surface low pressure systems brought above-normal precipitation to parts of the Southwest, parts of the Pacific Northwest to Great Lakes, and parts of the Southeast, Upper Ohio Valley, and Northeast. But the speed and tracks of the weather systems left much of California and other parts of the West, most of the Central to Southern Plains, parts of the Southeast and Northeast, much of the Mid-Mississippi Valley, and Mid-Atlantic coast drier than normal. Temperatures averaged cooler than normal in the West under the influence of the troughs, while the dominance of ridging east of the Rockies resulted in above-normal temperatures. As noted by the U.S. Department of Agriculture (USDA), the persistence of the unseasonably warm weather east of the Rockies has ushered winter wheat out of dormancy up to a month ahead of normal. The warm temperatures and unusually early green up have increased evapotranspiration and heightened the need for soil moisture in areas wrestling with winter-time drought, at a time when crop-water demands are typically minimal. As reported by the National Weather Service, vegetation has responded rapidly to the unusually warm temperatures, with flowers and trees blooming or in full bloom across east-central Georgia and central South Carolina. Drought conditions continued to improve in California, as the hydrologic systems responded to the precipitation of recent weeks and months, and in the Northeast. Drought and abnormally dry conditions expanded from the Southern Plains and Midwest to the Southeast and Mid-Atlantic coast, reflecting precipitation shortages that have developed over the last one to three months as well as, in the Southeast, worsening hydrological conditions and long-term dryness. The Northeast to Mid-Atlantic: Weekly precipitation amounts ranged from 1 to 2 inches across parts of New York, Pennsylvania, and Vermont, to a tenth of an inch or less across coastal New England and much of Pennsylvania and New Jersey southward to Virginia. D0 in New York, and D1 in northeast New York and northern Vermont, were pulled back where precipitation was wetter than normal this week and at many longer time scales. But the much warmer-than-normal temperatures rapidly melted a significant amount of New England snowpack. Snow melting this fast pretty much just ran off into the rivers and streams as opposed to slowly entering the ground to recharge the ground water. An oval of D2 was introduced around the D.C. area where the 30-day precipitation was less than half an inch and significant deficits have built up over the last 12 months. D1 and D0 were expanded around the D2, and D0 expanded across most of Virginia. According to February 27 USDA reports, 44% of the pasture and rangeland in Virginia was rated in poor to very poor condition.
The Southeast: One to 2 inches of rain fell across parts of Mississippi to Georgia, and parts of Florida, by the USDM cutoff date, with 2-4 inches across southern Alabama. But precipitation was below normal across the rest of the Southeast, with less than an inch of rain over eastern Tennessee and less than half an inch across western Tennessee, parts of Florida, and much of Georgia and the Carolinas. D0-D2 were pulled back in southern Alabama and west-central Georgia where the heaviest rains fell. The rain over northern Mississippi was not enough to show improvement, but did stave off any further drought expansion this week, while D0 expanded in southwestern Mississippi. D0-D3 expanded across parts of Tennessee. D0-D2 expanded in the Carolinas, and D3 crept into the western Carolinas. Very dry conditions were evident in many drought indicators, including record low streamflow and record low precipitation. The last 12 months (02/29/16-02/28/17) have been the driest such 12-month period on record for over a dozen stations in the southern Appalachian area, including Asheville, Mt. Mitchell, Tryon, and Waynesville in North Carolina; Anderson, Laurens, and Walhalla in South Carolina; and Cedartown, Elberton, Hartwell, Helen, Rome, and Toccoa in Georgia; it was the second driest for a dozen more stations. Similarly, over a dozen stations in the western Carolinas and northern Georgia had the driest 6 months on record for 8/28/16-2/28/17. The North Carolina Division of Water Resources well and baseflow analysis classified parts of western North Carolina at exceptionally dry levels. Low water levels were reported in Anderson County, SC, where Lake Hartwell s level was dropping. Several soil moisture models indicated exceptionally dry soils in the western Carolinas, with February 27 USDA reports showing 50% of North Carolina's topsoil and 25% of the subsoil short to very short of moisture, and 24% of the pasture and rangeland in poor to very poor condition. But, since it is early in the growing season and few crops have developed, agricultural impacts were not showing up yet. At this time, water systems and water supply were adequate and reservoir levels in western North Carolina were still good. The D3 in the western Carolinas reflected the current record low streamflows and record dry precipitation, as well as drying soils. The South: An inch to 2 inches of rain fell across parts of southern Arkansas and northeast Louisiana this week, but generally less than a tenth of an inch to no precipitation occurred across most of the rest of the South. D0 was shaved in southwest Oklahoma to reflect heavy precipitation from previous weeks which wasn t accounted for last week. But expansion of D0- D2 occurred across parts of Oklahoma, Texas, and Arkansas, while D0 expanded across the northern half of Louisiana into adjacent southwest Mississippi. February 27 USDA reports indicated that topsoil moisture was short or very short (dry to very dry) across 42% of Oklahoma and 33% of Texas, and subsoil moisture was short or very short across 43% of Oklahoma and 30% of Texas. Pasture and rangeland were in poor to very poor condition across 37% of Oklahoma and 20% of Texas, while some crops were suffering at this early stage. In Oklahoma, 21% of the canola, 27% of the oats, and 15% of the winter wheat were in poor to very poor condition. Midwest: With precipitation for the week below normal by the Tuesday morning cutoff, D0 expanded across the lower Ohio Valley to southwest Ohio and across parts of Kentucky to reflect dry conditions at the 7- to 120-day time scales. D0-D1 expanded across Missouri. February 27 USDA reports indicated that 46% of the subsoil and 51% of the topsoil in Missouri, and 27% of the subsoil and 28% of the topsoil in Illinois, were short or very short of moisture.
Central to Northern Plains: Bands of precipitation fell across the Central to Northern Plains. Much of Kansas and parts of the Dakotas received a tenth of an inch or less of precipitation, while a snowstorm dropped 0.3-1.0 inch of precipitation across parts of Nebraska and southwest South Dakota. D1 expanded across eastern Kansas, while D0-D1 contracted in northwest Nebraska and western South Dakota. According to February 27 USDA reports, 56% of the subsoil and 55% of the topsoil in Kansas, and 30% of the subsoil and 25% of the topsoil in Nebraska, were short to very short of moisture, while 21% of the winter wheat in Kansas was in poor to very poor condition. California: Two or more inches of precipitation fell across parts of the northern California coast, the Sierra Nevada, and San Diego County regions, while less than an inch was recorded in other areas. The typical interior rainshadow areas had less than half an inch of precipitation. Drought improvement occurred in three regions. The D0-L in the San Joaquin Valley was removed due to improving hydrological (aquifer) conditions. There are two types of aquifers: confined and unconfined. Unconfined aquifers are characterized by a geology where water can seep into the aquifer from the ground surface directly above. Confined aquifers have a geology in which an impermeable layer of dirt or rock exists above the aquifer which prevents water from seeping into it from the ground surface directly above. Confined aquifers are recharged by water seeping into them from farther away where the impermeable layer doesn't exist. Most of the USGS well groundwater stations in the San Joaquin Valley were showing significant recharge occurring, while those that were still quite low were probably confined aquifers which may take months or years to recharge. D1 was pulled back along the Coastal Range to Santa Barbara County. The lake levels of the reservoirs in Santa Barbara and Ventura Counties continued to rise but, since the rains let up, they were not rising as quickly. Lake Cachuma s reservoir was at 87,466 acre-feet on February 26, which equates to 45.2% of capacity versus 42.4% a week ago; Lake Casitas was at 43% compared to last week s 42.3%; and Lake Piru was at 33.7% versus last week s 31.7%. D2 was kept in place in this region to reflect the continued low, but recovering, reservoirs. However, the recent rains have not improved the situation on the offshore islands. With below-normal precipitation this week and continued groundwater shortages, D2 was added to Catalina Island. Rain during the last day of this USDM week gave southern California and southwest Arizona a good soaking, with rainfall amounts 0.5-2.0 inches over parts of Arizona and over 5 inches over parts of San Diego County in California. In the mountains of San Diego County, Palomar Observatory reported 9.04 inches of precipitation. D0-D1 was pulled back one category in San Bernadino, Riverside, and San Diego counties, and the adjacent D2 was trimmed a bit. The rain should result in rapid responses in local reservoirs. The San Diego River reached 14.2 feet, which is the third highest stage ever and slightly higher than December 2010 and 1980. Rest of the West: One to 4 inches of precipitation fell across coastal Washington and Oregon and parts of the Northern to Central Rockies, the Great Basin, and Arizona. Less than an inch of precipitation fell across other parts of the West, with some areas receiving a tenth of an inch or less. D1 was deleted and D0 contracted in eastern Oregon and western Montana to better reflect precipitation and snowpack conditions. D0-D1 was trimmed in southwest Arizona and D0
pulled back in east-central Montana. D0 was added over the southwest mountains of Montana to reflect low snowpack water content (SWE) and subnormal precipitation at the 7-day to 3-month time scales, and D0 was expanded over northeast New Mexico to better reflect soil moisture and streamflow conditions. Hawaii, Alaska, and Puerto Rico: The week was wetter than normal across much of Alaska, except drier-than-normal conditions dominated in the panhandle and south-central coastal area. D0 expanded into the Anchorage area and the Kenai Peninsula where SNOTEL SWE was low and 30-day to 6-month precipitation deficits dominate. D0 added to the southern coast of Puerto Rico, where soil moisture was dry, and to the eastern third of the island, where precipitation and streamflows were low. December through February (to date) precipitation at San Juan was 74.7% of normal. Bush fires have been reported along the southern slopes of Puerto Rico, which is near normal for this time of year, but reservoirs were still in good shape. Much of Hawaii was drier than normal this week. According to the FSA, some farmers in the Kona area have been hauling water for their cattle, but the current depiction for the Big Island adequately represents those conditions, so no change was made to the depiction for Hawaii. Looking Ahead: In the 2 days since the Tuesday morning cutoff time of this week s USDM, a frontal system dropped 1-2 inches of rain, and locally more, across parts of the Ohio Valley D0 area, with half an inch or more falling across parts of the Southeast. For March 2-9, 3-5 inches of precipitation, and locally more, is forecast for north coastal California to western Washington; 1-2 inches over parts of the Northern Rockies; and a tenth of an inch or more across the rest of the Northwest into the Great Basin. Precipitation is expected across parts of the Southern Plains to Southeast, Northern Plains to Great Lakes, and along the Eastern Seaboard, with amounts ranging from a few tenths of an inch across most of these regions, to an inch or two across southern Texas, the Gulf Coast, and northern Great Lakes. Most of the Southwest into the Central Plains should be dry. Above-normal temperatures are expected for most of the CONUS, with the greatest departures in the Central Plains, while below-normal temperatures may linger in the Pacific Northwest. Odds favor the temperature anomaly pattern persisting through March 10-15, with cooler-than-normal temperatures expected for Alaska. March 10-15 projections favor a continuation of the precipitation anomaly pattern with belownormal precipitation from the Southwest to Central Plains and along the Gulf of Mexico coast to Mid-Atlantic States, with above-normal precipitation favored for the rest of the CONUS. Odds favor drier-than-normal weather in southern Alaska and wetter-than-normal conditions in northern Alaska. Author: Richard Heim, NOAA National Centers for Environmental Information 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 Drought D2... Severe Drought D3... Extreme Drought D4... Exceptional Drought Drought or Dryness Types S... Short-term L... Long-term Updated February 7, 2017