Pittsburgh residents should brace themselves for an umbrella-demanding day. The National Weather Service forecasts widespread rain across the region and temperatures climbing well above the norm for this time of year. Rainfall will persist until late tonight and may culminate with light snow showers as it tapers off. In the wake of this soggy parade, cooler but dryer conditions are slated for Saturday.
Besides drenching the city, the rain is poised to accelerate the local snow-melting process, potentially flooding area streams and rivers, especially those south of Pittsburgh. According to the National Weather Service, rain falling on frozen ground, which cannot absorb the moisture, is expected to increase runoff significantly. High temperatures could stubbornly push past the 50-degree mark, especially across the southern half of the forecast area, which holds a 60%-100% probability.
Looking ahead to tonight, the rain will end from north to south as drier air moves in. There's an outside chance that a few snowflakes will choose to mix in on the northern side of the rain shield. Fast forward to Saturday, and Pittsburgh should see a sunnier sky with temperatures near seasonal averages, thanks to high pressure and a brief bout of cold air advection.
For the aviators among us, widespread MVFR/IFR restrictions in the rain are forecasted this morning through the evening due to an incoming low-pressure system. Dry slotting and weak subsidence may limit rain to areas near or south of KMGW through 15z but increase coverage between 15z-21z. Pilots should be aware that fog could remain a potential hazard due to the abundance of moisture and melting snow on the ground. The cold frontal passage is expected to be between 20-23z, bringing a chance of showers and brief gusty winds, followed by a temporary visibility improvement near 00z.
Regarding hydrology, the Mon, Yough, and Cheat River basins could see significant rises in water levels as a blend of rainfall and snowpack runoff causes disturbances. While forecast points are expected to hit the action stage, none are projected to reach the minor flood stage, per the National Weather Service's analysis. Meanwhile, the Allegheny Basin is less heavily impacted, though ice jam flooding remains possible as water levels are predicted to rise this weekend.
