Daily Archives: Friday, June 27, 2025 9:29 am

Philadelphia Area Weather Forecasts

WEEKEND WEATHER FORECAST

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Friday and the Weekend Preview

The backdoor cold front that pushed through on Thursday has become stationary to our west and our south.

Fri 10:11 AM – Sorry folks, something was clearly wrong with the data I was looking at an hour ago for this forecast. Showers have broken out just west of the city. The RRFS that I was looking at showed nothing all day! Maybe that’s why they call the RRFS experimental”
Nexrad Radar at 10:11 AM (Click on image for a larger view.)

The RRFS forecast for the same time frame shows nothing!

00z RRFS Simulated Radar forecast for 10:10 AM. It shows nothing for our area! (Click on image for a larger view.)

What’s most disturbing- the NWS announced just yesterday that they’ll be retiring several models (NAM, HREF, HIRESW, NARRE) when the RRFS becomes operational in early 2026. See my RRFS page.

There is ongoing development of the RRFS where the plan is to take it from its current FV3 core to the MPAS (“model prediction across scales”) geometry. Here’s the highly experimental RRFS MPAS forecast for today which over-forecast the rain to our south, but captured these showers-

MPAS RRFS developmental model. For this, raw data is not available to the public. This is a NOAA graphic) (Click on image for a larger view.)

It’s not clear if the first operational release will be with the FV3 core or the MPAS core.

Originally Posted Fri 9:29 AM —

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. I’ve drawn in the approximate position of the stationary front.

As a result, Water Vapor Temperatures indirectly reveal height, called the “effective layer” of the water vapor in a region, therefore revealing the mid and upper level 3D contours of systems.. Colder temperatures (blue- grey – white) indicate higher altitude, sometimes revealing upward motion. Red- Orange indicates warmer temperatures and a lower height for this layer. There are several water vapor “channels”; the one I display here is called the mid level height channel.   (Click on image for a larger view.)

For today, Friday, a cool, stable easterly flow will keep skies cloudy, but the RRFS does have some sun filtered through high and mid level clouds early afternoon. Except for a quick possible sprinkle, the Philadelphia region should remain dry today.

Clouds return late afternoon and evening as the stationary front moves northeast as a warm front.

Saturday will have clouds in the morning, possibly with some showers, sprinkles and fog, then breaking for sunshine and increased humidity and temperatures as the warm front moves north. Showers and thunderstorms possible Saturday night, especially after midnight.

Sunday becomes sunny and quite warm, humid. Details will depend on the actual position and movement of the warm front.

Despite the unsettled and changeable weather this weekend, I don’t see much in the way of widespread substantial rain around Philadelphia

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