A severe thunderstorm watch is in effect until 4 p.m. Wednesday as a flood advisory for the Ohio River continues, according to the National Weather Service in Moon Township.
The thunderstorm watch area includes Allegheny, Armstrong, Beaver, Butler, Fayette, Greene, Indiana, Washington and Westmoreland counties.
A watch is issued when conditions are favorable for the development of severe thunderstorms in and close to the watch area. A severe thunderstorm by definition is a thunderstorm that produces one inch hail or larger in diameter and/or winds equal or exceed 58 miles an hour.
A flood advisory also is in effect for the Ohio River at Pittsburgh. The river at the Point is forecast to rise above 18 feet by Thursday evening, which will flood the Monongahela parking wharf.
The National Weather Service forecasts the river to crest around 18.5 feet by early Friday morning, then fall below 18 feet by Friday evening.
Here is the NWS forecast:
Wednesday: Showers and possibly a thunderstorm. Some storms could be severe, with damaging winds. High near 65. Breezy, with a south wind 16 to 22 mph, with gusts as high as 32 mph. Chance of precipitation is 90 percent. New rainfall amounts between a quarter and half of an inch possible.
Wednesday Night: Rain showers before 3 a.m., then a chance of rain and snow showers between 3am and 4am, then a chance of snow showers after 4am. Low around 29. Breezy, with a south wind 15 to 24 mph becoming west after midnight. Winds could gust as high as 37 mph. Chance of precipitation is 90%. New snow accumulation of less than a half inch possible.
Thursday: A chance of snow showers before 10am, then a slight chance of snow showers after 5pm. Cloudy, with a high near 31. Breezy, with a west wind 20 to 23 mph. Chance of precipitation is 30%. Little or no snow accumulation expected.
Thursday Night: A chance of snow showers. Cloudy, with a low around 15. Light west wind increasing to 9 to 14 mph after midnight. Chance of precipitation is 40%.
Friday: A chance of snow showers, mainly before 1pm. Cloudy, with a high near 20. West wind around 18 mph, with gusts as high as 28 mph. Chance of precipitation is 40%.
Friday Night: Mostly cloudy, with a low around 11.
Saturday: A chance of snow showers after 11am. Cloudy, with a high near 24. Chance of precipitation is 50%.
Saturday Night: Snow showers likely. Cloudy, with a low around 20. Chance of precipitation is 60%.
Sunday: A chance of snow showers. Mostly cloudy, with a high near 28. Chance of precipitation is 40%.
Sunday Night: Mostly cloudy, with a low around 18.