Skip Navigation Links 
NOAA logo - Click to go to the NOAA home page National Weather Service   NWS logo - Click to go to the NWS home page
Climate Prediction Center


July - September 2010


Outlook Graphic: GIF   PDF Adobe PDF Reader


Latest Seasonal Assessment - Recent late-season rainfall eroded moisture deficits in some core drought areas of the interior Northwest, but further improvement during the climatologically drier summer season is less likely. Enhanced chances of above-median precipitation during the second half of June for the northern Rockies may further ease drought conditions in northern Idaho, while drought persistence is expected across the remainder of the region. Drought persistence is also expected across the west-central Great Basin where the summer months are climatologically drier, though some short-term improvement is possible in south-central Oregon. Further south, monsoon-generated thunderstorm activity might bring some improvement to drought areas in Arizona and New Mexico. Across the upper Mississippi Valley and Great Lakes regions, thunderstorm and MCS activity may locally increase topsoil moisture, but significant improvement of the multi-year hydrological drought remains uncertain. To the south, although short term forecasts indicate dry, hot conditions across the southern Plains states and lower Mississippi Valley, daily air-mass thunderstorm development and the potential for tropical-cyclone related moisture influxes maintain prospects for some drought improvement. Drought conditions are expected to persist and expand across interior Alaska, and climatologically drier conditions across the leeward side of the Hawaiian islands will promote drought persistence.

Discussion for the Seasonal Drought Outlook

Tools used in the U.S. Drought Outlook (USDO) included the official CPC precipitation outlook for July 2010 and the long lead forecast for July - September 2010, various medium- and short-range forecasts and models such as the 6-10 day and 8-14 day forecasts, the soil moisture tools based on the GFS model and the Constructed Analogue on Soil (CAS) moisture, the Climate Forecast System (CFS) seasonal precipitation forecasts, climatology, and initial conditions.

In recent weeks, the Upper Midwest has received beneficial rainfall, and stream flows have accordingly been given a much-needed boost. Additional heavier rain events will be needed however, to overcome what has been a long-standing, nearly two year drought in some areas such as northern Wisconsin. Prospects for substantial mitigation of drought are anticipated to improve during the next two weeks and into July, especially for the western and central portions of the drought area, based on extended-range predictions of an upstream upper-air trough and multiple opportunities for precipitation. However, eastern Upper Michigan and northern Lower Michigan have reduced odds of receiving above-median rainfall during the same period, and therefore persistence of drought conditions is deemed the most likely outcome. In the longer ranges, the odds favor neither abnormally wet nor dry conditions. During the summer season however, frontal boundaries and thunderstorm complexes tend to affect this general area, but it is nearly impossible to tell this far ahead how much of an impact these factors may have on the regional drought.
Forecast confidence for the Upper Midwest and northern Michigan is low to moderate.

Moderate to severe drought continues across northern and central sections of Louisiana, and small areas of bordering states. This drought is particularly noticeable at longer-ranges, according to departure from normal precipitation maps for the past 90-days and past 180-days. The official CPC monthly precipitation outlook for July indicates no discernible tilt in the odds for either abnormally wet or dry conditions. CPC's July-September 2010 precipitation outlook however, favors above-median rainfall in this area. Scattered airmass thunderstorms are a common occurrence across the lower Mississippi Valley in the summertime, and across the Southeast in general, which will likely result in very localized, spotty relief. Another consideration for this Drought Outlook in the lower Mississippi Valley is the NOAA forecast of an active tropical cyclone season in the Atlantic basin. Some improvement in the drought is therefore anticipated across this region, but confidence is low. The small area of moderate drought in southwestern Oklahoma is expected to see some improvement as well.
Forecast confidence for the lower Mississippi Valley and southwestern Oklahoma is low.

Abnormally wet conditions have prevailed across the northern and central Rockies during the past few weeks. USGS stream flow gauges throughout this region are primarily reporting flow values that are close to normal for this time of year. Experimental soil moisture forecasts based on CFS model ensembles support a slow drying trend over the next few months, which is generally consistent with CPC's official monthly and seasonal precipitation outlooks. The July 2010 precipitation outlook calls for no significant tilt in the odds for abnormal wetness or dryness in this drought area. In August and September, it will be very difficult to overcome dry summertime climatology. Therefore, most of this drought area is predicted to persist throughout this period, with the exception of limited improvement expected in the second half of June across northern Idaho.
Forecast confidence for the northern and central Rockies is moderate.

In the Southwest, very little rain has fallen over the moderate to severe drought area encompassing northern and central portions of Arizona and New Mexico. Even though dryness is favored in the ensuing few weeks, much will depend thereafter on both the strength and duration of this summer's monsoon, which at this time is unknown. The experimental soil moisture forecasts based on CFS model ensembles support initial wetness in July, with a gradual drying trend throughout August and September. The most likely scenario would favor some improvement across the desert Southwest.
Forecast confidence for the Southwest is moderate.

In the far West (west-central Great Basin), light amounts of rain have fallen in recent weeks. Given we are now in the hot, dry summer season, it will be extremely difficult to overcome regional climatology. Therefore, persistence of drought conditions is anticipated for nearly all of this area, with the exception of south-central Oregon, where some improvement is expected in the shorter-term.
Forecast confidence for the far West is high.

Moderate to extreme drought continues across the leeward sides of the Hawaiian Islands. Forecasts for these areas call for below-median rainfall during the July - September 2010 season, leading to drought persistence. In addition, with this typically being a drier time of the year, it is difficult to see how drought amelioration may come about, excluding of course, any tropical storms or hurricanes.
Forecast confidence for Hawaii is high.

Moderate drought persists in the central Interior of Alaska, and has been accompanied by a significant number of early season wildfires. Localized summer thunderstorm activity in the Interior is often accompanied by little rain, lightning, gusty winds and small hail, the first two of which are particularly dangerous in heavily wooded conifer forests. In addition, drought is expected to expand across most of the central Interior during this period. The CPC Precipitation Outlooks valid for the month of July, and the July - September season, do not show a tilt in the odds for either abnormally wet or dry conditions for this area.
Forecast confidence for Alaska is moderate.

NOAA/ National Weather Service
NOAA Center for Weather and Climate Prediction
Climate Prediction Center
5830 University Research Court
College Park, Maryland 20740
Page Author: Climate Prediction Center Internet Team
Page last modified: June 17, 2010
Information Quality
Privacy Policy
Freedom of Information Act (FOIA)
About Us
Career Opportunities