April-June 2006

Latest Seasonal Assessment - An extremely dry winter has resulted in the development of moderate to extreme (D1-D3) drought across much of Arizona and New Mexico, as well as extreme southern Colorado. The drought was record breaking in some areas, such as Phoenix where no measurable rainfall was observed for 143 consecutive days. The dry, warm weather resulted in little if any snowpack across in the mountains. However, an early March storm brought relief to parts of the region and generated the first significant precipitation in several months. Additional drought relief is expected during the first few weeks of the outlook period. Despite the short term relief, the dry season is just around the corner and the region will not receive enough rain and snow to make up for the record dryness. Therefore, temporary short term relief will be followed by drought persistence. Over the southern Plains, extremely dry, warm conditions over the past six months have resulted in the development of severe to exceptional (D2-D4) drought. Further north, the drought is less severe over areas such as Kansas and Nebraska. During the final weeks of March, some relief is expected as storm systems bring welcome moisture to the region. However, there are indications that the spring will be dry and warm. As a result, the drought is expected to persist, with possible further expansion into eastern Colorado. Over the western Corn Belt, some drought relief is possible over the next few months, while drought development is possible across the Southeast and Mid-Atlantic. Drought is already underway in North Carolina and parts of Virginia.

Tools used in the Drought Outlook included the official CPC long-lead precipitation outlook for April-June, the drought termination and amelioration probabilities for June, various medium and short-range forecasts and models such as the 6-10 day and 8-14 day forecasts, and the soil moisture tools based on the GFS model and the Constructed Analogues for the season.

Very warm and extremely dry weather over the past several months across Texas and Oklahoma has resulted in the development of widespread severe to exceptional (D2-D4) drought. The drought has caused widespread wild fires, low water tables, low river levels and very low soil moisture levels across the region. The drought is raising concerns over the upcoming cropping season. During the past 5 months, less than a tenth of an inch of precipitation has been recorded at many stations in Oklahoma. Precipitation amounts over the past 365 days are 15 to 20+ inches below normal in places such as Tulsa, Oklahoma City, Dallas and San Antonio. Temperatures over the past 90 days have averaged some 5 to 8 degrees Fahrenheit above the long term mean in these cities. The warm and very dry weather has been observed in western Arkansas and southwestern Missouri, where the drought is causing wells to go dry. To the north, the drought is less severe over Kansas and Nebraska. However, top soil moisture levels are quite low in some areas. During the first few weeks of the forecast period, welcome moisture due to the passage of a storm system may result in some improvement. However, there are indications that the April through June period will be drier and warmer than normal over the southern Plains. As a result, short term improvement would be followed by the persistence and even intensification of the drought. Drought may expand into northeastern Colorado. However, over eastern Oklahoma, northeastern Texas, eastern Kansas, Arkansas and Missouri, the potential for significant rains during the first few weeks of the period should result in some improvement early in the period. To the north, moderate to severe (D1-D2) drought developed across southeastern Nebraska, southern Iowa, northeastern Missouri and northern Illinois due mainly to below normal rainfall during various periods in 2005. The spring is expected to result in some improvement across the Midwest. However, there are some concerns that drought could redevelop during the summer if La Niña persists.

An extremely dry, warm fall and winter season has resulted in the development of moderate to extreme (D1-D3) drought across Arizona, New Mexico and extreme southern Colorado. The drought resulted in record dryness in some areas. In Phoenix, for example, no measurable precipitation was recorded from October 19 through March 10. This resulted in 143 consecutive dry days and a completely dry November through February period, both of which has never been observed before. In New Mexico, November through February precipitation totals ranked in the lowest 3 percentile over more than half the state. Furthermore, the extremely dry weather has resulted in little if any mountain snowpack, even on the highest peaks. However, a storm system moved through on March 11-12, bringing the first bout of significant rain and snow to the Southwest in several months. Phoenix received about 1.4 inches of rain, while surrounding areas picked up as much as 3 inches or more. In the mountains, well over a foot of snow was reported. However, in New Mexico, the precipitation was much lighter. Less than a quarter of an inch of rain was reported in Albuquerque. Snowpack continues to be well below normal. Basin-averaged snow water equivalents are only 20 to 45 percent of normal across Arizona. Most of New Mexico has less than a third of the normal snowpack. In the Sangre De Cristo Mountains, Basin-averaged snow water equivalents are less than 20% of normal. The SNOTEL site at Sierra Blanca in southern New Mexico, at an elevation of 10280 feet, had no snow on the ground as of mid-March. Some relief is expected across Arizona, southern Colorado and portions of New Mexico during the first week or so of the period as storm systems cross the Southwest. However, the dry season begins soon, and the recent and anticipated storminess will not generate enough precipitation to make up for a record dry winter season. In addition, there are indications that the April-June period will be warmer than normal, thus increasing evaporation, snow melt and moisture demand. Therefore, temporary improvement during the first few weeks of the period will be followed by the persistence of moderate to extreme drought. To the north, the season has been good with normal to well above normal snowpack over northwestern Colorado, western Wyoming, western Montana, Idaho, Nevada, northern California and the Pacific Northwest. However, there are some exceptions. Snowpack in the Lewis and Clark Range west of Great Falls, Montana is running slightly below normal. This, combined with low snowpack in recent years has resulted in moderate (D1) hydrologic drought. Opportunities for additional snowfall and indications for a cool spring by various seasonal forecast tools should result in improvement. Improvement is expected across the D1 areas of northeastern Wyoming and South Dakota as well.

There are indications from GCMs and statistical guidance that precipitation for the April- June period will be below normal across much of the Mid-Atlantic and Southeast, including the Florida Peninsula. This could result in the development of drought across these areas. Conditions have been abnormally dry during February and early March across much of Virginia and the Carolinas. Moderate drought is underway across central North Carolina and portions of southern Virginia.