Pittsburgh (PBZ) — the National Weather Service forecast in plain English · Plaincast

What has changed

Update to Key Messages and Aviation Discussion.

Messages

Widespread rain and isolated thunderstorms expected early Saturday with new disturbance

Monitoring the potential for strong to severe storms Sunday evening with a cold front

Discussion

A weak shortwave will exit the region early this morning, allowing drier and quieter conditions to develop after 9am. No hazardous weather is forecasted for today.

A new disturbance, advancing from the south, will increase the potential for rain showers and thunderstorms Saturday morning and will likely continue into the evening hours. The primary threat with this system heavy rainfall, which could lead to localized flooding concerns. High-resolution models currently suggest the greatest flood potential will be south and/or southeast of Pittsburgh. High-resolution models indicate a 30-50% probability that forecasted rainfall amounts will exceed 6 hour flash flood guidance during Saturday evening. Swaths of 1 to 2 inches of rainfall could occur.

Deep ample moisture and weak shear, generally below 30kts, will reduce the risk for strong to severe thunderstorms Saturday. The lack of sufficient dry air will reduce the risk of damaging downdrafts. Lightning will likely remain the secondary hazard during the afternoon and evening hours.

The risk for moderate to heavy rainfall will decrease early Sunday morning as the disturbance exits east and drier air aloft increases.

There is the potential for strong to severe thunderstorms Sunday afternoon and evening as a trough and associated cold front quickly move across the Great Lakes. Machine-learning guidance indicates a 5-15% chance of severe weather for a portion of our region. Long-range ensembles support 50-60% joint probabilities of effective shear above 30kts and storm energy values above 500J/kg during the afternoon and evening hours, with highest probabilities noted north of Pittsburgh where stronger vertical wind shear resides.

If the system continues to evolve favorably across the region, all severe weather threats, including damaging winds, hail, and tornadoes, will be possible.