Daily Archives: Friday, July 11, 2025 8:11 pm

Philadelphia Area Weather Forecasts

WEEKEND WEATHER FORECAST

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Sunday Forecast Update

Posted Sunday 07/13/25 @ 8:58 AM — A strong high pressure circulation at the surface will block most thunderstorm formation in our area today. The latest water vapor image with RAP model superimposed shows the high circulation clearly—

Current satellite water vapor image with superimposed RAP model 500-1000 mb thickness lines (yellow), Mean Sea Level Pressure isobars (black contours) potential vorticity (fine violet contours) with superimposed MRMS RADAR. High pressure circulation at the surface (H) and upper level thickness ridge (yellow contour 573) will keep storms to our north and west today. (Click on image for a larger view.)

While many models are showing highs of ‘only’ 88º, I’m leaning towards the those that show nearer 90º. Dew points near or at 70º.

As has been the case, the experimental RRFS (and NAM-NEST) shows a few isolated showers northwest into Bucks and Montco around 6 PM. Likely over-done.

As a weak boundary moves towards us, a few showers and thunderstorms are possible in our area towards daybreak Monday.

Models reviewed for this forecast: GDPS-AI, NBM, RRFS , REFS, ECMWF-AI, HRRR, NAM-NEST

Saturday Forecast Update

Posted Saturday 07/12/25 @ 8:34 AM — Not much change from last night’s forecast posting. The Canadian GDPS with “AI Spectral Nudging” still has some pop up showers between 4 PM and 9 PM; most of the area will be dry. Here’s the total forecast coverage of the showers—

GDPS forecast Total rainfall coverage between 4 PM and 9 PM (5 hour time frame. ) The shading is 0.2″ to 0.7″. (Click on image for a larger view.)

Most areas will see temps 89º-91º The NBM has dew points in the uncomfortable 72º range. The GDPS-AI has dew points in the upper 60s at the height of the temperature range.

Sunday looks partly sunny and dry; no rain in our area until after midnight.

Originally Posted Fri 8:11 PM —A typical summer pattern will be with us through the weekend. Warm, humid each day. A chance of pop-up storms late afternoon, but most of the area will be dry.

Reviewing Friday’s forecast, some pop-up storms developed in South Jersey, but did not move far westward. As mentioned, the REFS has a tendency to over-forecast convective rainfall. Looking back, the new Canadian GDPS with “AI Spectral Nudging” was spot on with the today’s weather and I’ll lean on it for this weekend’s forecast.

Saturday Forecast

Cloudy with some fog in the morning. Clouds lift for sunshine by late morning through the afternoon. A few pop-up thundershowers possible about 7 PM

12z GDPS with “AI Spectral Nudging” forecast for 7 PM Saturday. Clouds are dark/grey and black contours.. Most areas will see no rain. (Click on image for a larger view.)

NBM high temperatures: Blue Bell, PA 89º Philadelphia, PA 90º
Higher than average uncertainty (based on standard deviation): ± 2.4º

Sunday Forecast

Sunny. Some clouds far west. Showers possible far western sections in the evening.

NBM high temperatures: Blue Bell, PA 89º Philadelphia, PA 90º
Average uncertainty (based on standard deviation): ± 1.5º

Models used for this forecast: NBM RRFS GDPS with “AI Spectral Nudging”