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Climate Prediction Center


June - August 2010


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Latest Seasonal Assessment - Drought continues in parts of the interior West, though recent rains have eroded moisture deficits in the northern Rockies. Through mid-June, additional improvement is expected in the northern Rockies, with more modest improvement anticipated in the central Rockies. Farther south and west, drought should persist through the forecast period, which covers a relatively dry time of year, in Nevada and adjacent parts of California and Oregon; however, increasing odds for monsoon-related rainfall is expected to bring at least modest improvement to the established drought in northeastern Arizona. To the east, protracted drought in the Great Lakes region and emerging drought in both the southeastern Plains and upstate New York should either persist (in the eastern Great Lakes and upper reaches of the southeastern Plains) or modestly improve (elsewhere) depending primarily on rainfall amounts forecast through mid-June, since the longer-range outlooks are non-committal in these areas. Finally, drought should persist and expand across interior Alaska, and persist through the relatively dry summer months in leeward sections of Hawaii.

Discussion for the Seasonal Drought Outlook

Tools used in the U.S. Drought Outlook (USDO) included the official CPC precipitation outlook for June 2010 and the long lead forecast for June - August 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.

Moderate drought developed in upstate New York in late May. Moderate precipitation is anticipated into the second week of June in the region, but the various outlooks covering mid-June through August favor neither wetness nor dryness, and climatology likewise does not tilt wet or dry relative to other times of the year. In sum, a forecast for some improvement is the path of least regret, but with low confidence.
Forecast Confidence in upstate New York is low.

Moderate to severe drought continues in a significant swath from northeastern Minnesota and western Wisconsin eastward across the northern Great Lakes region. In parts of northern Wisconsin particularly, drought has become entrenched over the course of a few years. Western and central sections are forecast to see enhanced rainfall through mid-June, but amounts look to drop off farther east. In the longer ranges, the odds favor neither abnormally wet nor dry conditions, and climatology would favor some limited improvement at this time of year, especially in western parts of the region. Still, given the entrenched nature of the drought in most of the region and the lack of any indications of either wetness or dryness in the longer ranges, a low-confidence forecast for drought to persist in eastern sections and for limited drought improvement farther west seems most prudent, differentiated by short- and medium-range outlooks and to a lesser extent by climatological precipitation patterns relative to other times of the year.
Forecast confidence for the Upper Midwest and northern Michigan is low.

Drought continues across much of Louisiana, easternmost Texas, and adjacent areas in early June. Moderate to heavy rainfall into the second week of June should improve conditions somewhat in southern sections of both Louisiana and eastern Texas, but dryness is forecast for the medium range, and the June - August forecast favors neither dryness nor wetness. Given the volatility of precipitation patterns in this region during summer and with some consideration of the forecast for an active tropical season, low confidence for some improvement seems the forecast of least regret in southern parts of the region where early June is expected to be wet, with a low confidence forecast for persisting drought farther north.
Forecast confidence for the southeastern Plains is low.

In recent weeks, a series of winter-like storms has moved across the western portion of the U.S., improving drought conditions from western Wyoming northward through western Montana and, to a lesser extent, parts of Idaho. With odds favoring above-normal rainfall through June, additional drought improvement is expected in the short to medium range, with the best odds centered on western Montana and central Idaho. Despite all of these positive signs, however, this remains a difficult forecast. The areas expected to see some of the most substantial precipitation through June also have increased odds for subnormal June - August precipitation, muting forecast confidence. In sum, drought is forecast to improve across western Montana, northern and central Idaho, and northern Wyoming while more limited improvement is indicated in southeastern Idaho, farther south in western Wyoming, and adjacent Utah where precipitation through June is expected to be less robust. Furthermore, forecast confidence is reduced due to summer climatology, which does not favor improvement. The bottom line for this area is that the contradictory nature of the indicators does not allow for a high confidence forecast.
Forecast confidence for the central and northern Rockies is moderate.

In northeast Arizona, little change is expected in drought conditions through June. By later in the summer, however, monsoonal moisture will begin triggering showers and thunderstorms in these areas, and while the strength of the monsoon relative to typical years is uncertain, climatology indicates that at least some improvement is likely.
Forecast confidence for northeast Arizona is moderate.

Drought continues from central Nevada northwestward through northeastern California and southern Oregon. Summer is a relatively dry time of year for the region, and while the odds tilt slightly toward above-normal rainfall in the northwesternmost reaches of the region both for early June and for the month as a whole, improvement is not climatologically favored at this time of year.
Forecast confidence for the area of existing drought in Nevada, California, and Oregon is moderate.

Moderate to extreme drought continues across the leeward side of the Hawaiian Islands. Forecasts for these areas call for below-median precipitation during the June - August season, leading to drought persistence. Also, the islands are entering the drier time of the year, making drought amelioration all the more difficult.
Forecast confidence for Hawaii is high.

A small area of moderate drought developed as June got underway in interior Alaska, and abnormal dryness currently exists in most of central and interior southern Alaska. Snow water content was well below normal across this region (at or below 50% of normal). Odds favoring below normal precipitation during the 6-14 day period combined with typically-increasing summer temperatures and the fact that forecast odds favor warmth for the June - August period all lead to a forecast for drought persistence and expansion.
Forecast confidence for Alaska is moderate.

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Page Author: Climate Prediction Center Internet Team
Page last modified: June 3, 2010
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