Drought in Virginia, May 1 to 31, 1999

High pressure was the dominant weather feature across Northern Virginia during the month. This weather pattern directed rain producing low pressure systems north of the region and continued the climatological drought that has gripped the area since last summer. By the last week of May the Palmer Drought Index, a measure of long term drought conditions, indicated Northern Virginia was in a moderate drought. May was the 7th month in the past 12 months that precipitation was below normal. Only 2.22 inches of rain fell at Dulles International Airport in Loudoun County during the month of May, 1.80 inches below normal. It was the 8th driest May on record, and rain only fell on 5 days during the month. Additional rainfall totals included Frederick County at 1.5 inches, Shenandoah County at 2.9 inches, Warren County at 1.4 inches, Rockingham and Orange County at 2.4 inches, Augusta County at 3.0 inches, Highland County at 2.2 inches, Nelson and Albemarle County at 2.3 inches, Culpeper County at 2.8 inches, Rappahannock County at 2.1 inches, Fauquier County at 2.2 inches, Spotsylvania County 0.5 inches, and Fairfax and Loudoun County at 2.0 inches. The lack of rainfall affected water levels along the Potomac River, the main water source for extreme northern Virginia. The flow of water past Washington D.C. hovered around the 10th percentile and record low daily flows were reported in some upstream tributaries. Monthly flow rates of the Potomac River have been below average for the last 9 months. During May, the average daily flow of the river was only 38% of the long term average. Conditions on the Shenandoah and Rappahannock River were also extremely dry. Some stations in these two watersheds reported streamflow at or below the 90th percentile exceedence, which rivaled minimum daily mean flow values of the drought of 1980-82. With such low water tables, Spotsylvania County was forced to reinstate voluntary water restrictions. The Ni River Reservoir, main water source for the county, had already dipped 4 inches below the spillway by mid month. The lack of precipitation also played havoc with spring planting and livestock maintenance. Trees were prematurely shedding leaves in orchards, hay and pastureland were wilting, and watering holes and irrigation sources were slowly drying up. 69% of pastureland and 58% of hay across the state was reported in poor or very poor condition. 58% of of topsoil was reported as short or very short of moisture by the end of the month. Some farmers had to reduce their herd sizes in order to stretch hay and water supplies. In addition to agricultural lands, forests and rural vegetation was also dangerously dry. In Page County alone, fifteen brush fires were reported in May near Stanley, including one that burned 100 acres. Another fire in Shenandoah National Park burned around 400 acres and closed a 40 mile stretch of Skyline Drive for several days during the first week of the month.