Weather Update Fri 11 PM
Tonight’s NAM and WRF models have scattered thunderstorms as early as 3 pm Saturday. In the immediate Philadelphia area, it seems that the most activity and the strongest dynamics will be between 5-8 pm.

Sunday may have significant cloudiness, as mentioned below.

Today’s thunderstorms did materialize and dissipated as expected about 8 PM.

The heat will be with us through Saturday. A front will move through on Saturday, the result of an upper low pressure system dropping down over the New England coastline.

There are significant differences between the GFS global model and the mesoscale models regarding showers and thunderstorms Saturday afternoon. The GFS has the showers remaining in the  northwest suburbs and dissipating before reaching the immediate Philadelphia area.

The mesoscale models (NAM, WRF and the HIREF ensemble) have showers and thunderstorms moving through Philadelphia late Saturday afternoon and evening.

The mesoscale WRF and HIREF models did well today and I’m leaning towards their forecast, but the discrepancy between the GFS and these models can’t be overlooked.  So confidence in the chance of showers in Philadelphia Saturday is below average.

Most models are forecasting high temperatures Saturday 92-94 with high clouds and increasing lower level cloudiness during the afternoon. It will be humid. If the WRF and HIREF are correct, showers are likely far northwest suburbs mid afternoon and they move through Philadelphia between 4-8 PM.

Sunday will have a mix of sun and some clouds. The upper low cyclonic flow may result in more clouds than currently forecast. It will be breezy. High temps 86.

I’ll update later this evening after 11pm when the new model runs come in.