Monthly Archives: March 2025

Philadelphia Weather Outlook

THIS WEEK’S WEATHER

#Philadelphia #weather #PAwx

Posted Thursday 03/06/25 @ 5:42 PM — The MRMS total rainfall graphic I posted in yesterday’s “Forecast Review” was posted before the storm had fully exited our area. Here’s the final rainfall totals for the region, which are impressive—

MRMS rain-gauge measured rainfall combined with rain-gauge calibrated and interpolated radar-based summary of ACTUAL RAINFALL RECEIVED. Color shading is in inches. Line contour numbers are in mm. (25.4 mm= 1 inch)      (Click on image for a larger view.)

There isn’t much happening weather-wise over the next several days and into next week. We’ll be in a colder upper trough for some of the weekend. The next storm to affect our region may be next Thursday or Friday.

Wed 7:49 PM —Forecast Review —The majority of the rain has ended in the immediate PHL area. (There’s still heavy rain in NJ at this time.) Some additional showers are still possible this evening, Here is the MRMS rainfall summary for today’s rain.

The total rainfall was considerably greater than forecast by the models. The GFS was notably off.

MRMS rain-gauge measured rainfall combined with rain-gauge calibrated and interpolated radar-based summary of ACTUAL RAINFALL RECEIVED. Color shading is in inches. Line contour numbers are in mm. (25.4 mm= 1 inch)      (Click on image for a larger view.)

It’s been a long time since we had such a heavy rain event.

Wednesday Forecast Update

Posted Wednesday 03/05/25 @ 4:16 PM — The HRRR, despite being a little slow with the first batch of rain, did well with the main line. Here’s what the radar looked like at 4:13 PM—

Radar image 4:13 PM. Very similar to the HRRR forecast shown below for 4PM (Click on image for a larger view.)

Posted Wednesday 03/05/25 @ 11:30 AM — Current radar shows the leading edge of rain much closer than the HRRR model has forecast. Even the 15z (10 AM EST) HRRR doesn’t show this.

I would expect the leading edge of the rain to be into Philadelphia within the next two hours. There is a line of heavier rain entering central PA. That might be the line of storms the HRRR is predicting for 5 PM.

Posted Wednesday 03/05/25 @ 8:25 AM — The models are consistently showing a strong line of storms with heavy rain and gusty winds to 50 mph coming through the city about 4 PM-

06z HRRR showing instantaneous precipitation rate at 4 PM

Addition showers possible during the evening hours. The actual cold front doesn’t come through until 2 AM Thursday morning.

Wednesday Forecast Update

Posted Tuesday 03/04/25 @ 8:49 PM — Tonight’s HRRR continues with a forecast of a line of storms moving through Philadelphia between 3 and 4 PM.

At 2 PM, the line is to our west, but with some break-out showers ahead of the main line—

Tonight’s 00z HRRR forecast for 2 PM Wednesday. The line is over Philadelphia at 4 PM. (Click on image for a larger view.)
Tuesday -Wednesday Forecast Update

Posted Tuesday 03/04/25 @ 9:14 AM — The models are forecasting these early morning clouds to dissipate by late morning. High temperatures 58º Blue Bell to 60º in the city.

The rain on Wednesday is now forecast to begin somewhat later in the morning as light showers. The heaviest rain now appears to move in about 3-6 PM with potential thunder and wind gusts approaching 50 mph.

Here’s the latest HRRR Precipitation Rate forecast—

Today’s 12z HRRR Precipitation Rate forecast for 5 PM Wednesday. (Click on image for a larger view.)

Posted Monday 03/03/25 @ 4:57 PM —A low pressure system is developing in the Rockies and will move northeast bringing rain on Wednesday. Here’s the current water vapor image—

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. (Click on image for a larger view.)

The latest models show a consistent forecast of rain moving in around 6-8 AM Wednesday. Before that time, warmer air ahead of the system will be with us on Tuesday with sunshine through high clouds. Highs on Tuesday 53º -56º (high uncertainty: ± 3º)

The rain on Wednesday is much-needed and the AI models are forecasting about 0.80 inches of rain, more far northwest and less into NJ. The deterministic ECMWF is similar, with localized 1″ amounts. The GFS model is only forecasting about 0.50 inches of rain, less into NJ. There may be pockets of heavier rain due to localized thunderstorms. Some high wind gusts possible beginning mid-afternoon Wednesday.

A cold front moves through about 1 AM Thursday morning. There may be lingering shower activity Thursday morning in eastern sections of NJ.

Originally Posted Sun 7:43 PM —Another cold day on Monday, followed by a warmup on Tuesday with temperatures rebounding into the low to mid 50s.

A storm is expected to move across the country and affect our weather on Wednesday with rain developing before daybreak.

18z 03-02-25 GFS forecast for Wednesday at 3 PM (Click on image for a larger view.)

We need some rain and unfortunately, the trend of the past few storms looks to continue, with the heaviest rain occurring to our far northwest.

This afternoon’s GFS shows the heaviest rain to occur to our far northwest on Wednesday. (Click on image for a larger view.)

Another trend has been for the predicted rainfall in our area to diminish with each subsequent model run. Yesterday, the total rainfall was predicted to be in the 0.8-1″ range around Philadelphia. The latest GFS posted above (in agreement with the ECMWF) has about half that amount forecast. (The latest ECMWF AI model still has about 0.8″ of rainfall here.)

I wish I could identify why this trend is occurring. It’s been going on since late last Spring.

Cooler weather returns for Thursday