Monthly Archives: March 2025

Philadelphia Weather Outlook

THIS WEEK’S WEATHER

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#Philadelphia #weather #PAwx

Yet Another AI Model ‘Experiment”

The latest ECMWF-AI mode (single) and the latest GFS have very different forecasts for Wednesday and Thursday regarding cloud cover. An easterly flow behind a back door cold front may result in very cloud conditions.

Here’s the latest GFS cloud cover for Thursday noon—

18z GFS forecast for Thursday noon. Very cloudy and damp. (Click on image for a larger view.)

Here’s the ECMWF-AI-Single forecast for Thursday noon—

12z ECMWF-AI Single has little to no low clouds. Plenty of sun through high thin clouds. (Click on image for a larger view.)

The two forecasts couldn’t be more different regarding cloud cover. Ordinarily, with these forecasts, I would go with the GFS model. (The GFS relative humidity fields support a very dark cloudy mid-day. The NAM-NEST also is forecasting low clouds. )

The ECMWF-AI-Single model has really impressed me regarding temperature forecasts. It’s also done well with rainfall. Let’s see how Thursday’s cloud cover turns out. (Or whether the models come together.)

Posted Monday 03/10/25 @ 5:07 PM —A large ridge of high pressure in the central US with a split jet flow moving around this central high will continue to bring above average temperatures to our area.

Current (Monday afternoon) 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. Warm upper air ridge in center of the US. Split jef flow. The disturbance to bring rain late Saturday isn’t visible yet in this image. (Click on image for a larger view.)

Dry weather is expected to continue until late Saturday afternoon or evening.

Previously Posted Sun @ 5:03 PM — —The big story (and actually the only story) for the weather this coming week will be the warmer temperatures expected. Additionally, winds and wind gusts will be considerably lower than recent days.

For Monday, here’s the latest model blend (NBM). What’s interesting is how close the the ECMWF-AI model is to the NBM model with less computational effort.

18z NBM forecast high temperatures for Monday (Click on image for a larger view.)

By Tuesday, warmer temperatures push in from the southwest. We’ll be in the 67º-69º —

ECMWF-AI Single model temperatures at 2 PM Tuesday. (Click on image for a larger view.)

It’s been well-advertised about the 70º temperatures for this coming Saturday. The latest AI model suggests we may not reach that.

The change to Daylight Saving Time always takes some adjustment. For me, the biggest adjustment is the one hour later availability of weather model data. One hour doesn’t sound like much, but it brings models out a bit too late in the morning to be as useful and too late in the evening to make the 11 PM TV weather. I’ve written about this many times over past years—

Little Known Facts about Daylight Saving Time and TV Weather Forecasts

Daylight Saving Time and Weather Models

“Check Back at 11” — TV Weather and Daylight Saving Time

Philadelphia Area Weather Forecasts

WEEKEND WEATHER FORECAST

#Philadelphia #weather #PAwx

High pressure continues to build in for the weekend, as low pressure departs to our northeast—

Latest GFS shows high pressure moving southeastward . Departing low pressure with highly packed isobars to our northeast continues to move away.

The storm track is to our south over the next several days. Winds diminishing somewhat by Sunday—

18z NBM wind meteogram for Blue Bell PA (Click on image for a larger view.)

Saturday Forecast

Sunny and continued windy and gusty. Wind gusts approaching 30 mph during the afternoon.

NBM high temperatures: Blue Bell, PA 47º Philadelphia, PA 49º
Average to low uncertainty (based on standard deviation): ± 1.4º

Sunday Forecast

Sunny and windy, but less so than Saturday.

NBM high temperatures: Blue Bell, PA 52º Philadelphia, PA 54º
Low uncertainty (based on standard deviation): ± 1.0º