Saturday morning’s NAM has backed off on the showers in eastern PA but has a slight chance for widely scattered showers in central NJ Saturday morning. Lingering periods of cloudiness in the morning still expected.
Tonight’s NAM data is just becoming available and it has the front lingering over our area during Saturday morning. This is a large change in the forecast. So there’s a chance of lingering light, scattered showers during the morning hours tomorrow, Saturday. Skies improve in the afternoon.
(GFS data not available until much later due to daylight saving time, so I can’t compare models at this time)
A weekend forecast that appeared high confidence, now appears to have some new uncertainty.
A front will move through Philadelphia late this afternoon and early evening (Friday) with showers and thunderstorms. Some storms are developing ahead of the front this afternoon in the warm, humid air. The dynamics suggest the possibility of heavy thunderstorms in PHL, although the strongest dynamics may move through to our north.
Updated 9 PM Fri: The heaviest storms were well north of the Philadelphia area. Rainfall was less than forecast. The sky appearance was impressive
By Saturday morning, the front will have moved off the coastline resulting in sunny skies with gradually falling humidity/dew points as the day goes on. Highs will be around 86 with a light wind out of the west.
For Sunday, some cloudiness very early, then partly to mostly sunny. Lower dew points in the 60s and highs around 85.
A return to unsettled weather and humidity for early next week.
As mentioned in a previous forecast, with an upper closed low, the models rarely accurately predict the placement of the heavy rains and such was the case yesterday. In fact, all of the models over-predicted rainfall, including the EMCWF (European). Most areas in PHL and immediate surrounding areas only had 0.75 to 1 inch of rain. The heaviest rain was in Maryland and near Baltimore.
(When it snows, everyone knows when the forecast QPF isn’t correct; when it rains, fewer people realize it.)
For today, Sunday, the NAM has some hazy sunshine breaking out by morning or early afternoon. But it also shows high instability in the early afternoon with showers as early as 2 PM. The chance of showers continues thorough the evening. These will be random and scattered.
The GFS LAMPS has increased chance of showers and thundershowers in the late afternoon. The experimental NBM (National Blend of Models) has a high chance of showers and some embedded thundershowers during late afternoon (4 PM) and evening, as does the EMCWF.
So, not a washout, but unsettled, with showers especially likely after 4 PM into the evening.
This morning’s models haven’t changes significantly. Widely scattered showers are now in Delaware. The short range models have the rain moving into the immediate Philadelphia between noon and 2 PM, earlier to the south. The rain continues into the late evening, heavy at times.
The axis of the heaviest precip shows some variation among the models, with areas just to our south and areas of NJ having the heaviest. It’s very difficult to pin point the exact placement of the heaviest precipitation.
Sunday is currently looking relatively dry, with only very widely scattered showers; most of the area rain free.