The Hydrologic Services Area (HSA) encompasses portions of four states:
Western Pennsylvania The northern panhandle of northern West Virginia East Central Ohio
Garrett County Maryland
The Monongahela, Allegheny and Upper Ohio River are the primary streams in this HSA.
These form the headwaters of the Ohio River. Major tributaries include the Beaver, Clarion, Cheat,
and Youghiogheny Rivers. In December 1994, the Pittsburgh HSA added most of the Muskingum River
basin in East Central Ohio to its HSA.
HSA rivers flow through many heavily-populated river valleys, including the city of
Pittsburgh. Pittsburgh is the largest inland port in the nation. When seaports are considered,
Pittsburgh ranks 11th. Commercial barge traffic on the primary streams has a significant impact
on the economy of the four-state region. According to a Port of Pittsburgh Commission study
released in July 1996, these rivers generate nearly 120,000 jobs and $5.2 billion in wages annually.
Most commonly, hydrologic problems occur when heavy rain falls over moderately
steep/mountainous headwater areas, resulting in flash flooding in narrow, populated valleys.
Among the nation's fastest responding mainstem river systems, flooding on the
HSA's rivers occurs when synoptic-scale systems bring widespread rainfall. Ice jams and
moderate rainfall on snow during the cooler months can also produce significant flooding.
The Pittsburgh HSA has over forty forecast points. Forecast guidance is provided by the
Ohio River Forecast Center (OHRFC) in
Wilmington, Ohio. In addition to daily river stage forecasts, the Pittsburgh Forecast Office issues
River Ice Statements at least twice weekly during ice season.
weather.gov 
