Pittsburgh will see periods of rain with potential localized flooding in some regions
Storms brought very heavy rain to portions of Western Pennsylvania and Northern West Virginia on Saturday. Isolated 1-3"+ swaths of rain occurred along our I-80 counties and in portions of Washington and Monongalia counties, which prompted flash flood warnings.
WEATHER LINKS:
Current Conditions | School Closings & Delays | Submit Your Weather Photos
There were reports of water rescues and flooded properties around the South Strabane area in Washington County late Saturday night, but water levels have since receded in that area. Similar to what occurred yesterday, we expect a very similar setup once again for Sunday afternoon, with some locations completely missing rain, while others get drenched and face a flash flood threat.
Sunday morning begins with plenty of dense fog along the I-79 and straddling most of the Ohio Valley. This fog is expected to continue through around 9 a.m. Moisture levels remain very high, not only near the ground, but throughout a large depth of the atmosphere this morning and will continue to do so through the afternoon. A parameter we look at to assess the amount of moisture in the atmosphere is expected to creep up to the 90th percentile later this afternoon for areas near and especially southwest of Pittsburgh.
While this doesn't guarantee everyone will see a washout, these slow-moving scattered storms that do form will produce very heavy rain and flooding in spots. In fact, most areas north of Highway 422 toward I-80 may stay completely dry today. The timing window of today's rain will occur between 12 p.m.- 9 p.m. Flash flooding will be a concern for locations that receive greater than 0.75"-1" of rain within an hour.
The highest rainfall amounts—again in isolated, localized areas—could reach 3-4+".
Once we lose daytime heating, any thunderstorms that are ongoing will fall apart after sunset with mostly cloudy skies and a few remnant showers tonight into Monday morning. Patchy dense fog is expected again before we heat up and isolated to widely scattered storms form during the midday and evening hours of Monday. Highs will reach the upper 70s to low 80s.
The biggest change in the forecast has been to increase rain chances for this upcoming Tuesday. All model guidance has started trending toward showing a wave of low pressure moving in from the west early Tuesday morning into Tuesday afternoon. This system would provide lift in an already very moist atmosphere to produce more heavy rain and localized flooding.
Most of the rain on Tuesday will likely occur from the late morning through mid-afternoon hours. This system will move east by Wednesday, leading to a lower coverage of rain during the day.
Southwest winds will bring in very warm & humid air ahead of another stronger storm system and cold front Wednesday night into Thursday. This will carry a risk of severe storms and flash flooding. Slightly drier and cooler air will filter in on Friday.
Stay up to date with the KDKA Mobile App – which you can download here!