The Southeast: Heavy showers continued to erode dryness and drought from the lower Mississippi Valley into parts of the Southeast. The Delta region of Mississippi received as much as 4 to 10 inches of rain during the first two weeks of July, eradicating or significantly reducing the coverage of abnormal dryness and moderate drought (D0 and D1). By July 15, USDA rated Mississippi’s topsoil moisture 81 percent adequate to surplus and 19 percent very short to short. Two weeks earlier, on July 1, those Mississippi numbers had stood at 15 percent adequate to surplus and 85 percent very short to short. Farther east, in Muscle Shoals, Alabama, precipitation during the first half of 2007 totaled just 11.97 inches (40 percent of normal), but July 1-14 rainfall reached 6.25 inches (234 percent).
Rainfall was lighter and more scattered farther to the north and east, where a core area of extreme to exceptional drought (D3 to D4) persisted across large parts of Tennessee, northern Alabama, and western Georgia. Nevertheless, conditions gradually improved for pastures and many later-planted summer crops. From July 1 to 15, the amount of pastures rated very poor to poor improved from 86 to 68 percent in Alabama, 68 to 52 percent in Georgia, 72 to 66 percent in Tennessee, and 62 to 55 percent in Kentucky. More dramatic two-week improvements in very poor-to-poor pasture conditions were noted in Mississippi (from 66 to 11 percent) and Florida (from 60 to 20 percent). In terms of row crops, Alabama’s two-week improvements included 74 to 55 percent very poor to poor for cotton and 64 to 38 percent for peanuts.
The Northeast: Conditions primarily remained unchanged or deteriorated across the northeastern and mid-Atlantic states. In particular, three areas of moderate drought (D1) were blended to make a continuous area stretching from eastern North Carolina to the vicinity of Lake Erie. In addition, a new area of severe drought (D2) was introduced in the mid-Atlantic coastal plain. In Virginia, the percentage of pastures rated very poor to poor surged to 67 percent by July 15, up from 48 percent two weeks earlier. Farther north, enough rain fell in southern Maine to reduce the coverage of abnormal dryness (D0).
The Midwest: Little change in the moderate drought (D1) situation was noted in the eastern Corn Belt, while abnormal dryness and moderate drought (D0 and D1) expanded across the upper Midwest. By July 15, USDA indicated that 20 to 30 percent of the corn and soybeans were rated very poor to poor in Indiana, Michigan, and Ohio. Crop conditions were also beginning to slide in the upper Midwest, where the percentage of Minnesota’s corn rated very poor to poor jumped from 8 percent on July 1 to 19 percent two weeks later. During the 25-day period from June 23 to July 17, less than one-tenth of an inch of rain fell in locations such as Sioux Falls, South Dakota, and Marshalltown and Sioux City, Iowa.
The High Plains: Some severe drought (D2) was introduced on Montana’s High Plains due to record-setting heat and diminishing moisture reserves. Cut Bank, Montana (106 degrees F on July 6), noted its hottest day since August 5, 1961, when an all-time record of 107 degrees F was established. It was easily Cut Bank’s hottest July day on record (previously, 103 degrees F on July 19, 1960). Spring-sown small grains began to suffer in the Treasure State, with the amount of Montana’s spring wheat rated very poor to poor climbing from 6 to 18 percent between July 1 and 15. During the same period, the amount of barley rated very poor to poor in Montana rose from 11 to 26 percent.
In the adjacent mountainous region of western Montana, Missoula endured a historic heat wave during the first 17 days of July. Missoula’s highs reached or exceeded 100 degrees F on July 5-6 and 12-16 (seven days total), breaking its 1936 annual record of six days. From July 1-17, Missoula’s streak of 17 consecutive 90-degree days was its second-longest heat wave behind an 18-day such hot spell in 1960. Meanwhile, poor vegetation conditions and low reservoir levels led to an expansion or introduction of severe to extreme drought (D2 to D3) in an area centered on southwestern South Dakota.
The West: Record-setting summer heat waves have been common across the West in recent years, and 2007 has been no exception. Most recently, intense heat struck the Northwest, where all-time-record highs in Washington included 99 degrees F (on July 10) in Hoquiam and 94 degrees F (on July 11) in Bellingham. Seattle, Washington (98 degrees F on July 11), experienced its hottest day since July 20, 1994, when an all-time, record-tying high of 100 degrees F occurred. Meanwhile, the onset of the southwestern monsoon (officially, July 8 in Tucson, Arizona, based on a dewpoint definition) contributed to numerous lightning strikes and a corresponding increase in western wildfire activity. During the first 17 days of July, western wildfires charred nearly 1.7 million acres of vegetation, doubling the nation’s year-to-date total to 3.4 million acres (125 percent of the 10-year average).
Western heat and drought has also taken a toll on pastures, rangeland, and rain-fed summer crops. According to USDA, rangeland and pastures were rated at least 40 percent very poor to poor on July 15 in the following states: California (96 percent), Nevada (64 percent), Arizona (57 percent), Utah (46 percent), and Oregon (40 percent). In Washington, crops rated at least 20 percent very poor to poor included spring wheat (34 percent) and barley (24 percent).
Aside from agricultural impacts, much of the West continued to experience long-term drought and water-supply concerns. At the end of June, water storage in the Colorado River system stood at 9.09 trillion gallons, just 65 percent of average. Lake Mead, near Las Vegas, one of the two huge reservoirs along the Colorado River, held 4.15 trillion gallons (63 percent of average). By mid-July, the 1,112.6-foot elevation of Lake Mead’s surface represented a near-record low level. Prior to the current drought, Lake Mead was last below 1,125 feet in 1965. Lake Mead’s 1939-2003 average August elevation was 1,176 feet, while the record-low level dipped just below 1,100 feet in 1964. Elsewhere, end-of-June statewide reservoir storage stood at 73 percent of average in Oregon (27 of 31 reservoirs reporting) and 76 percent in Utah (25 of 28 reservoirs reporting).
Puerto Rico: Only light showers dotted Puerto Rico, leaving intact an area of long-term, hydrological dryness (D0H) across eastern portions of the island.
Alaska: Some heavy showers, locally in excess of two inches, fell along the northwestern fringe of the abnormally dry (D0) area over interior Alaska, resulting in a small reduction in the coverage. Alaska’s year-to-date wildfire total climbed above 200,000 acres, and the largest current blaze was the 3,500-acre Big Creek fire in the vicinity of Ruby (west of Fairbanks near the Yukon River).
Hawaii: Most of Hawaii’s leeward areas remained in moderate to severe drought (D1 to D2), following a disappointing wet season. Through July 17, year-to-date rainfall totaled just 2.69 inches (28 percent of normal) in Honolulu, Oahu, and 3.99 inches (35 percent) in Kahului, Maui. Meanwhile, Hawaii’s windward locations were still abnormally dry (D0). On the Big Island, Hilo’s March 1 – July 17 rainfall totaled 22.85 inches, or 48 percent of normal.
Looking Ahead: Weather that could have an impact on drought areas in the next two weeks: 1) a cold front will edge across the midwestern and mid-Atlantic states on July 19-20 before stalling across the South, preceded and accompanied by scattered thunderstorms and trailed by cooler, drier air; 2) scattered showers associated with the monsoon (summer rainy season) will dot the Four Corners States, while frontal rain will fall in the Pacific Northwest; 3) however, the majority of the Intermountain West will continue to experience unfavorably hot, mostly dry weather for the next several days; 4) the NWS 8- to 14-day outlook for July 26 – August 1 calls for unusually hot weather across the northern half of the U.S., excluding the Pacific Northwest, while cooler-than-normal conditions will prevail across the nation’s southern tier; 5) during the same July 26 – August 1 period, drier-than-normal weather across the midwestern, northeastern, and mid-Atlantic states will contrast with above-normal rainfall in southern Florida, the south-central U.S., and parts of the West.
