UNL Drought Monitor Update - 11/20 - Sonny's Prayer-Fest Didn't Help, It Seems . . .

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National Drought Summary -- November 20, 2007

The discussion in the Looking Ahead section is simply 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 NWS forecast products utilized include the HPC 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/.

A couple cold fronts and associated upper-level troughs brought precipitation to portions of the drought areas in the Pacific Northwest, northern Rockies, and eastern U.S. The rest of the nation remained generally dry. Cold temperatures followed the first front as it moved east of the Rockies. But month-to-date temperature anomalies remained well above normal across the western two-thirds of the country, with below-normal temperatures confined to the East.

The Southeast and Mid-Atlantic: The heaviest rains from the cold front early in the U.S. Drought Monitor (USDM) period fell across the western portions of the southern and central Appalachians, where reports of 1 to 2 inches were common. D4 was pulled back in eastern Tennessee and the southwest tip of Virginia where the heaviest rains fell. The rest of the Southeast and mid-Atlantic drought areas received generally 0.25 inch or less, with some areas recording up to an inch. But this was mostly insufficient to improve the long-term hydrological deficits which ranged from 10 to 20 inches since the first of the year across much of the area. Year-to-date deficits exceeded 20 inches from central Alabama to southwest North Carolina. Wells, springs, and streams were failing, and producers continued to reduce or liquidate cattle herds. All along the Tennessee River system, the Tennessee Valley Authority has announced it will not perform its usual winter draw down of reservoirs since they are already down to that level. D3 and D4 were expanded in southern Alabama and D1 expanded slightly in Virginia around Roanoke. D1 grew along the Gulf Coast of Florida, from Fort Myers to Beverly Hills, to reflect low streamflows. Low levels in the Peace River threatened drinking water supplies for communities in southwest Florida.

In spite of rains of recent weeks, major drought impacts were being felt across central and western North Carolina, where 14 local water systems have less than 100 days of water supply. Many streams were at or near record low levels and groundwater levels continued to reach record lows. The reservoirs that feed the population centers of the Piedmont Triangle region were nearing record lows. Consequently, D4-D3-D2 expanded eastward across North Carolina and the adjoining parts of South Carolina and Virginia.

The primary drought impact across much of the nation this time of year is hydrological. While the growing season for many crops has ended and the dry conditions were favorable for harvesting some crops, other agricultural interests were suffering from the drought, so an area of AH impacts was added to the Southeast this week. USDA reports indicate that planting of oat and winter wheat crops was behind schedule in South Carolina, and the lack of moisture continued to delay pasture growth, tobacco market preparations, and winter wheat germination in Tennessee. In Georgia, dry soil conditions continued to plague livestock and small grains producers, and farmers that had already planted new crops were in desperate need of rain. Winter forages and ryegrass in Mississippi were suffering due to the dry weather conditions. In Alabama, newly planted winter grazing was in desperate need of rain. In North Carolina, winter wheat was 69% planted on November 18, which is about average, but emergence was only 33%, well behind average. Topsoil moisture was rated short or very short across much of this region, from 68% of North Carolina to 86% of Georgia. Generally two-thirds of the pasture and rangeland was rated poor to very poor regionwide.

The Great Lakes and Ohio Valley: Frontal rains dropped an inch or more along and south of the Ohio Valley, and half an inch of precipitation fell across parts of the Great Lakes, otherwise precipitation amounts were light. D0 expanded southward along Lake Michigan in Wisconsin and Michigan, and southward in southeast Michigan to reflect low precipitation and modeled soil moisture conditions. D0 grew into southwestern Indiana to more accurately reflect modeled dry soil moisture conditions and long-term rainfall deficits.

The Northeast: An inch or more of precipitation fell across a large part of the Northeast this period, but the heavier amounts generally missed the drought areas. Modeled soil moisture indicated dryness remained in central Pennsylvania, so the D0 there was left in place. However, D0 in western New York was pulled back from Jefferson and northern Oswego counties.

The Plains: Heavy rains fell over southeast Texas late in the period, resulting in elimination of D0 from areas receiving about 2.50 inches or more. Half an inch of precipitation was observed in the northern Plains. But most of the Plains, otherwise, were dry. Texas now has 79 counties with burn bans in effect, roughly twice the number from about 2 weeks ago. D0 expanded across the Panhandle and north central Texas and further in south central Oklahoma. Two spots of D1 were added, one in southwest Oklahoma and adjoining Texas along the Red River, the other in northeast Texas-northwest Louisiana. In South Dakota, D1 expanded westward to the state line. D0 and D1 nosed a little westward in east central Montana to better reflect an area of below-normal precipitation at several timescales.

The West: A typical La Niña precipitation pattern characterized the West this period. Beneficial rain and snow occurred in the northern sections while the southern areas received little, if any, moisture. D1 and D2 retreated in eastern Washington and the Idaho Panhandle where half an inch or more of precipitation fell. Otherwise, no changes were made. Drought in the West is slow to develop and slow to end, and heavy mountain snowpack laid down during the winter snow season is the crucial drought-busting factor. Water-year-to-date precipitation is above normal along a swath from Oregon, across southern Idaho, and into northwest Wyoming, but with above-normal temperatures the precipitation is falling more as rain rather than snow. Northern Arizona is beginning to experience seriously declining streamflows, and water restrictions may become a possibility for some smaller communities later. However, it is early in the snow season, so no change was made to the depiction this week.

Alaska, Hawaii, and Puerto Rico: Conditions did not warrant any changes to the USDM depiction this week for these areas.

Looking Ahead: During the next several days, a strong Low pressure system and cold front will develop in the Ohio Valley and move to the Atlantic Coast, bringing beneficial rain and snow to the drought areas from the Southeast to Northeast. By the weekend, another Low will develop over the southern Plains and move across the Southeast, reaching New England by Tuesday and bringing another chance for beneficial rain to the southern and eastern drought areas. In the meantime, High pressure over the Great Basin will trigger dry Santa Ana winds across southern California. A Pacific storm system will move into the Northwest by the end of the period. A series of Pacific systems is expected to brush southern Alaska.

The outlook for November 26-December 4 calls for below-normal temperatures across most of the country, with above-normal temperatures for the Southeast and Alaska. Precipitation is expected to be drier than normal from the West to the Northeast, and across eastern Alaska, and wetter than normal from the southern Plains to the mid-Atlantic, and western Alaska.

Author: Richard Heim, National Climatic Data Center, NOAA/NESDIS

EDIT/END

http://drought.unl.edu/dm/monitor.html