Philadelphia Area Weather Forecasts

WEEKEND WEATHER FORECAST

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Sunday Update & This Week Outlook

Posted Sunday 09/14/25 @ 8:52 AM — The forecast of widely scattered showers today seems to have bit the dust. The over-forecast of precipitation remains a lingering issue with the experimental RRFS model. So expect mostly sunny with a few areas of cloudiness this afternoon.

As for the coming week, numerous TV/radio forecasts the end of last week were forecasting dry weather for this coming week. That was despite persistent AI model forecasts for a closed low and a westward, retrograding coastal surface low to bring rain to our area by Wednesday. I mentioned this last Friday.

Today’s water vapor shows the set up for this upper low/coastal low—

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. Water Vapor Imagery reveals emitted water vapor infrared TEMPERATURE, NOT REFLECTED LIGHT from CLOUDS. Upper low closing off- L BLUE Surface low already forming. L- Black. (Click on image for a larger view.)

The current ECMWF-AI forecast shows rain moving in as early as late Tuesday at the shore and into our area by early Wednesday. This is much-needed rain.

06z ECMWF-AI model forecast showing coastal low moving westward to join an upper air low pressure system. (Click on image for a larger view.)

Total forecast rainfall is currently is currently less than 1/2 inch. Perhaps that will increase?

Originally Posted Fri 6:10 PM —High pressure will continue to bring mostly sunny skies this weekend, however a few minor disturbances may bring a bit of cloudiness at times both Saturday afternoon and especially Sunday late afternoon.

Saturday Forecast

Mostly sunny, some cloudiness at times in the afternoon. A few very isolated light showers possible late afternoon.

NBM high temperatures:

18z NBM forecast high temps on Saturday. Grey shading is cloud cover at 4 PM (<50% in most areas.) (Click on image for a larger view.)

Sunday Forecast

Mostly sunny. Some clouds again in the afternoon. The experimental REFS and the RRFS once again show the chance of showers late Sunday afternoon—

12z REFS forecast for Sunday at 6 PM. Scattered showers due to a ‘short wave’ (Click on image for a larger view.)

The ECMWF-AI and the NBM do not show any showers.

NBM high temperatures show slightly greater uncertainty (higher standard deviation) than usual, possibly due to uncertainty in cloud cover.

18z NBM forecast high temps on Sunday. Grey shading is cloud cover at 6 PM (<40% in most areas.) (Click on image for a larger view.)