#Philadelphia #weather #PAwx #PhillyWx

Sunday Forecast Update

Posted Sunday 06/15/25 @ 9:35 AM — Last night’s NAM-NEST did well in predicting some of the heavier rain, although more fell in NJ than it had predicted.

As for today, little in the way of any rain is expected during the day, although mist, some fog and overall damp weather is expected.

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Posted Saturday 06/14/25 @ 8:27 PM —Sunday looks to be mostly cloudy with little in the way of rain in the Philadelphia region, based on the RRFS and HRRR,.

HOWEVER, at the other end of the spectrum is the NAM-NEST which has considerable rain in the morning and widely scattered showers during the day. This evening, the NAM-NEST forecast more closely matches the radar at this time lending credence to its forecast.

The latest ECMWF-AI model is closer to the NAM-NEST forecast.

So we have much significant uncertainty. As I often say, the most useful forecast is knowing the times when there’s little certainty.

If the RRFS and HRRR are correct, rain is expected to stay to our far north and to our far south. There may even be some breaks in the overcast and bright spots at times, especially in northern sections of the area. If the NAM-NEST is correct, there will be more showers throughout the day, especially in the morning.

Forecast models leaned towards: NAM-NEST ECMWF-AI

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Forecast Update

Posted Saturday 06/14/25 @ 9:17 AM — Last night’s 06z models (2 AM EDT) showed a trend towards less rainfall in the immediate Philadelphia area, not too different than the ECMWF forecast posted yesterday.

Here’s current radar around 9:30 AM—

Both the HRRR and experimental RRFS show this trend. This general trend has been consistent with some, but not all of the models. Here’s the 06z RRFS—

It should be noted that the Canadian HRDPS shows much heavier rainfall here around mid day. For now, we’ll ignore the HRDPS forecast.

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Previously Posted Fri @ 5:53 PM —A cold front has dropped south of our area today and become stationary. An easterly flow of cooler (but somewhat damp) air has moved into the region. The water vapor image from this afternoon captures the current scenario—

I should point out that the amount of sunshine we had today was greater than predicted by several models, and it sets into question whether the the current pattern is being properly modeled.

I’m going to provide several graphics of model forecasts at 2 PM Saturday to illustrate the wide range of rain coverage.

The most recent GFS forecast for 2 PM Saturday captures the extent of the rainfall, but I think it’s relatively low resolution suggests more rain than will actually fall.

A similar resolution ECMWF captures the more intermittent coverage of the rain—

The much higher resolution HREF model captures the more intermittent nature of the rainfall—

Finally, here’s the latest REFS (experimental) model forecast for 2 PM Saturday.

From all of these models, it should be apparent that there’s a wide range of rainfall coverage for Saturday, and with the exception of the GFS, the Philadelphia region and South Jersey appear to get the least rainfall.

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