July - September 2006 (Revised Outlook)

Latest Seasonal Assessment - The updated Outlook shows that the recently-worsening drought affecting parts of the northern Plains and the Upper Mississippi Valley should continue, and may even expand across eastern Montana, Minnesota, the Dakotas, and parts of Iowa. To the south, drought should persist over much of the central and southern Plains. In the Southwest and Colorado, heavy rains over the short term should ease drought conditions and reduce the danger from wildfires. However, long-term drought is likely to continue. Additional drought relief should visit southern and coastal Texas, but the outlook is less confident to the east. The drought affecting the northern Gulf Coast from Louisiana into Alabama and northwest Florida should benefit from periodic rains, although major improvement is not expected at this time. The drought in Georgia that extends into the western portions of the Carolinas may see improvement.

Tools used in the Drought Outlook included the official CPC long-lead precipitation outlook for July-September, the drought termination and amelioration probabilities for September, 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.

The June 15 Drought Outlook was updated on July 7 to reflect the worsening situation in the Northern Plains and Upper Midwest. The July 4 Drought Monitor brought D1 drought into much of North Dakota as well as northwestern Minnesota and northern Wisconsin. With medium-range forecasts showing above-normal temperatures for this region during at least the next 2 weeks, and generally light rains for the Dakotas westward into Montana for the next 10 days, there will be a tendency for drought to continue to expand. Latest model guidance shows that rainfall may be normal to above normal for Wisconsin and parts of Minnesota, so the greatest risk for drought worsening and expansion appears to extend from Iowa and western, central, and southern Minnesota westward into eastern Montana. For the longer term, the Constructed Analogue from Soil moisture (CAS) forecast tool indicates a tendency for dryness to persist across most of this region into autumn.

Elsewhere, the first 5 days of the period should see heavy monsoon rains extending from the arid Southwest into Colorado, and these rains will extend eastward into Kansas. The area of limited improvement shown in the updated Drought Outlook considers this shorter term outlook plus the Southwest seasonal guidance for July-September rainfall shown in the CDC regression forecast issued in June. The latter shows a weak tilt toward wetness for New Mexico and Colorado. More substantial drought alleviation for the Southwest will likely need to wait until the 2006-07 snow season.

The other main change from the June Outlook is toward less optimism for the central Gulf Coast and Deep South, where we have recently seen drought expansion in Alabama, Mississippi, and Louisiana. The rainfall outlook is very uncertain for this region for most time frames beyond the first few days. The week-2 bias-corrected GFS forecasts do show near normal rainfall for this region while longer-range forecast tools are mixed. Bottom line was a switch to a depiction of some improvement. Longer and shorter range forecasts look more optimistic for the drought extending from Georgia northward, so the forecast for improvement was continued from last month.