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Monday Forecast Update
Posted Monday 06/30/25 @ 9:07 AM — Yesterday’s Model Blend (NBM) proved to be correct about the lack of showers this morning, and I’ll stay with the NBM for today’s forecast, with individual models showing a range of forecast times for showers and thunderstorms.
Pop up storms can occur anytime after 1 PM today with peak activity between 5 PM and 8 PM.
The latest NBM shows activity near the city picking up about about 1-2 PM just east of the city.
A considerable increase in coverage will occur later in the afternoon. Some areas may receive heavy rain in a short period of time.
Likely focus of heavier storms will be central areas of South Jersey in the mid afternoon and areas north of the city in the late afternoon.
Originally Posted Sun 8:50 PM —The ‘cold’ front that moved through Saturday has stalled just to our south and thunderstorms have been breaking out in South Jersey for much of Sunday, especially near the Delaware Bay and Cape May.
The front will return as a warm front on Monday. Large differences in the forecast exist for Monday morning. The AI version of the ECMWF and the latest GFS have scattered showers breaking out early Monday morning, while the regular ECMWF, the AI version of the Canadian GDPS keeps us dry until 2-4 PM.
The experimental RRFS has scattered pop-up storms in the morning; this may be an example of its tendency to over-forecast convective rain.
The ECMWF-AI has so much precipitation and clouds in the morning that it keeps our high temperatures in the mid to upper 80s instead of the low 90s forecast by the drier forecasts.
The model blend (NBM) keeps us dry Monday morning as well, and I’m leaning towards its forecast. Its high temp in Philadelphia is 90.5º
It’s a tough call.
The models all come together by Monday afternoon with showers and thunderstorms popping up anytime between 1 PM and 4 PM and continuing into the evening. Peak time is about 6 PM according to the NBM.
Tuesday looks even more interesting, as a cold front moves into very moist and unstable air over the Philadelphia region. Stay tuned.