#Philadelphia #weather #PAwx

Weather Update

Posted Sunday 05/04/25 @ 9:40 AM — So far, the rain from this closed upper level low has not played out as forecast. Following the rain/thunderstorms last evening that just clipped the Phillies game, there hadn’t been much additional rain.

Some rain redeveloped this morning, just clipping the Broad Street Run, which wasn’t accurately predicted by any model.

Here’s the amount of rainfall from last night—

Currently two bands of rain exist, west and east of the city—

The latest RRFS is a good match for the current radar. It has more storms moving through 2=5 PM—

The models often correctly predict the overall general pattern with closed upper lows, but it’s also common for the details regarding rain banding and timing to be not very accurate.

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Forecast Update

Posted Saturday 05/03/25 @ 5:39 PM — Some fast moving isolated storms are developing just west of the city and in NJ, in areas having the greatest CAPE value. It’s a close call, but this evening’s storm development may remain away from Citizens Bank Park this evening.

Some rain will likely move in later this, with the heaviest precipitation still just west of the immediate Philadelphia area.

For the Broad Street Run, the models still keep a relatively rain-free period from 7 AM Sunday through about 11 PM. Rain then moves in from the south, with the heaviest bands again just west of the city.

Still A Difficult Forecast

Posted Saturday 05/03/25 @ 10:26 AM — The effect of the upper low has yet to affect the Philadelphia area. The upper winds are still anti-cyclonic in curvature, inhibiting rainfall. This morning, I’ve waited to see the latest models to post this forecast.

Here’s the latest water vapor image showing most of the immediate area rain free and no obvious triggers downstream—

This morning’s NAM-NEST, HRRR and RRFS keep any showers/storms to our far west, with sunshine through cirrus clouds for much of the day. Showers move eastward, just reaching the immediate Philadelphia area by late evening.

On the otherhand, the ECMWF-AI model along with the ECMWF and GFS have showers/storms moving in during the late afternoon and somewhat heavy activity this evening.

Here’s the GFS with showing rain developing as early as 5 PM—

A difficult forecast with such wide differences in model guidance. The AI model has been most consistent and the closest to reality, so I’m leaning towards its forecast of showers developing here late afternoon.

As for Sunday’s Broad Street Run, the models suggest a break in the rain from 7 AM to 11 AM, but heavier rain moves in from the south by 11 AM to noon. I’ll update later this afternoon.

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Includes forecast for Sunday’s Broad Street Run

Previously Posted Fri @ 5:34 PM — —The much advertised cut off upper level low takes shape late Saturday and will continue to affect our weather through Monday and possibly Tuesday.

The initial slug of energy is dropping south at this time and will close off as an upper level low over the Ohio/Mississippi Valleys.

A secondary surface low developing around Maryland will bring showers and thunderstorms Saturday evening into early Sunday morning.

The exact position of the upper low will determine if we are in the heavy rain bands expected to develop. The final position is not a certainty.

Some widely scattered showers and thunderstorms are breaking out a this time (Friday late afternoon) and there are indications that additional scattered showers/storms may develop this evening. Not all areas will see rain tonight.

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