AccuWeather.com

By Alex Sosnowski, Expert Senior Meteorologist

Sep 9, 2010; 2:00 PM ET

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A number of short-term and long-term factors are resulting in building drought conditions over a large part of the East. The dryness is also raising the risk of brush fires.

More than half of the 50 states are experiencing abnormally dry to drought conditions, according to the U.S. Drought Monitor's Sept. 7 release.

On the Eastern Seaboard, Virginia and North Carolina were experiencing the worst of the dry weather. However, recent dry conditions have a number of states creeping from abnormally dry conditions to moderate drought status.

This image appears courtesy of the U.S. Department of Agriculture. Yellow areas indicate abnormally dry conditions, while orange and red areas indicate areas of moderate to extreme drought respectively.

Very low humidity, combined with an active wind and little or no rainfall, is the more noticeable trigger.

The low humidity and wind raise evaporation rates, while there is no rain to replenish the moisture.

However, abnormal warmth since the spring may also be contributing significantly to the situation at the present time.

When temperatures are higher, evaporation rates are higher. Additionally, demand typically increases.

Much of the East has experienced average temperatures of 2 to 6 degrees above normal since the spring.

While some areas have had near-normal rainfall over the long haul, a number of areas have now slipped significantly below average in the rainfall department in recent weeks, and the above-normal warmth continues.

Pittsburgh, Pa., continues to experience above-normal warmth and below-normal rainfall. Temperatures have averaged 3 degrees above normal, while rainfall is just over 50 percent of normal, since Aug. 1.

Similarly, Charlottesville, Va., has been averaging around 3 degrees above normal for the same period. However, rainfall is under 50 percent of normal.

Portions of New England, New Jersey, Pennsylvania, Ohio, Indiana, West Virginia, Georgia and Alabama were included in the building dry or drought conditions.

Fronts and large-scale storm systems typically start to bring large areas of rain this time of the year. However, we have not really had much of this in the East so far.

Air mass thunderstorms, which typically decline in August due to the diminishing sun angle, become non-existent during September.

A batch of rain is forecast to move eastward from the Plains late in the week, reaching the East Coast later this weekend.

Potentially some of Tropical Rainstorm Hermine's moisture may be involved, especially in the central Appalachians.

It remains to be seen if this moisture fizzles as suggested by computer models, upon reaching the mountains.

The effects of the dry conditions go beyond low stream levels and brown lawns.

Some states and communities are asking people to voluntarily to conserve water usage.

Wind will be a problem in the Northeast into the evening, which could quickly fan any brush fires that get going, such as the one raging on Staten Island Thursday. It doesn't have to be hot outside to get a brush fires.

Be careful when using outdoor power equipment, grills, open flames and outdoor smoking.

Related to the Story:

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Global Warming Center

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