THIS WEEK’S WEATHER | Philadelphia Weekend Weather & Storm Forecasts

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No Snow Sunday

Posted Thursday 01/29/26 @ 5:34 PM — The models continue the trend in forecasting the coastal storm to move further to our east. Even the Canadian Global GDPS shows no snow for Philadelphia, where it had been showing 8″ a few days ago.

The forecast period now falls in the range of the higher resolution models (84 hours or less). Both the RRFS and the Canadian RGEM forecast to 84 hours and both show no snow for Philadelphia and even no snow for coastal NJ.

Here’s the latest RRFS precipitation forecast for Sunday—

18z RRFS forecast snow – closest approach. (Click on image for a larger view.)

The cold weather continues with temperatures possibly rising into the low to mid 30s by Monday. Another reinforcing cold front, perhaps with some light snow the middle of next week.

Sunday’s “Storm” Looking Less Likely

Posted Thursday 01/29/26 @ 10:24 AM — The latest models through the night and this morning continue to show the storm to develop near the coast to track to our east. Accumulations in the city and westward continue to trend less and less likely.

Here’s the latest Model Blend (NBM) which statistically evaluates over 40 models. 75 percent of the models show zero, or significantly below this value—

13z NBM just became available. Continues a trend towards minimal or no snow in Philadelphia and westward. Several inches possible near the Jersey shore. (Click on image for a larger view.)

NBM median shows half the models show this or less—

13z NBM median snowfall for Sunday (Click on image for a larger view.)

The NBM mean still shows some significant snow, meaning that 25% of the models show much higher amounts skewing the mean higher. They are outliers; still a possibility but not likely.

The storm is now falling into the range of the higher resolution models (84 hours) Here’s the very latest Canadian RGEM, showing the storm totally missing our area—

Today’s 12z Canadian RGEM forecast for Sunday 12 PM. Storm precipitation totally east of us. (Click on image for a larger view.)

Updates later today.

Sunday’s Possible Storm Update

Posted Wednesday 01/28/26 @ 7:34 PM — There continues to be a strong signal that the coastal storm expected Sunday will pass us by. The models in this camp continue to be the GFS, AIGFS, ECMWF-AI, ECMWF and the ICON model.

The Canadian GDPS with “AI Spectral Nudging” model still maintains a heavy snowstorm for us and the Global Ensemble models are still forecasting snow in the 3-5 inch range for Philadelphia.

The storm is still in the 96-120 hour forecast period and only the synoptic-scale global models extend their forecasts out that far; the higher resolution models come into play at 84 hours and less.

The latest model blend (NBM) statistical take on this storm is interesting.

The Median Snowfall is below and is currently my choice (perhaps with some blend of the 75 percentile) for this storm—

19z NBM median snowfall accumulation. 50% of the models show this or less. (Click on image for a larger view.)

The NBM 75 Percentile also captures the next 25% of the models—

19 NBM 75 percentile. **75% of the models are predicting this or less than this. Since the first 50% are predicting zero, for Philadelphia, only 25% are predicting 1-3 inches**, **the rest zero.** (Click on image for a larger view.)

Here’s the NBM MEAN snowfall which suggests that the remaining 25% of the models are predicting very high snow totals and is skewed high—

19z NBM Mean snow totals is skewed high due to 25% of the models showing heavy snow. (Click on image for a larger view.)

One of the models skewing the NBM mean high is the Canadian GDPS. It’s an outlier—

12z Canadian GDPS (Click on image for a larger view.)

Right now, I’m leaning towards the the NBM Median or a blend of the 75 percentile (zero-1″ in Philadelphia) based on the several models in that range. Stay tuned.

Sunday Storm Less Likely

Posted Wednesday 01/28/26 @ 11:13 AM — The current possibility of another major storm for Philadelphia is fading but not gone, especially for NJ. This current forecast of a Miller Type A nor’easter has demonstrated the power of a AI weather models with the AI models first showing the likelihood of a storm and also first showing the trend towards a more easterly track at our latitude.

The current forecasts, particularly with the ECMWF, ECMWF-AI and even the GFS and AIGFS have trended towards the storm entirely missing Philadelphia and/or only affecting mostly eastern NJ on Sunday. The German ICON model also has the storm well east of us.

A likely scenario is captured by the ECMWF-AI —

01-28-26 06z ECMWF-AI forecast for 1 PM Sunday. (Click on image for a larger view.)

On the other hand is the AI-ensemble hybrid HGEFS which still shows 2-3″ in Philadelphia. The westward extent is mostly due it the GEFS ensemble component to this model.

01-28-26 06z HGEFS forecast for 1 PM Sunday. Still a possibility of 2-3 inches in Philadelphia, but not a high likelihood. (Click on image for a larger view.)

This morning’s GFS, just available, captures the trend—

01-28-26 12z GFS forecast for 1 PM Sunday. The snow shield just brushes the coast of NJ. (Click on image for a larger view.)

The only model still showing substantial snowfall for Philadelphia is the Canadian GDPS with “AI Spectral Nudging” but it’s an outlier at this time.

The NBM mean snowfall incredibly shows 10″ in Philadelphia, but the current NBM does not include any of the AI models. The NBM median is closer to what some AI models are forecasting—

01-28-26 13z NBM median snowfall (Click on image for a larger view.)

So still some uncertainty. But a significant storm for Philadelphia continues to look less likely at this time based on the AI models. (Click on image for a larger view.)

Sunday Possible Storm Update

Posted Tuesday 01/27/26 @ 5:26 PM — Earlier I posted what was then the latest ECMWF-AI forecast, showing the expected nor’easter to graze the NJ shore this Sunday; the snow would not make it into Philadelphia.

The regular ECMWF and our own GFS models are currently moving in that direction. The latest GFS shows the storm’s snow shield barely making it into Philadelphia (but still showing ~1- 2 inches of snow.) The GFS predicts snowfall over 8-10 inches along the NJ shore.

01-27-26 18z GFS forecast for 1 PM Sunday. Snow barely makes it into Philadelphia, but significant snow possible at the shore. (Click on image for a larger view.)

The latest AIGFS is similar to the GFS forecast above. So we may be spared from a major snowfall. A 50 mile deviation in track would change this forecast dramatically.

Regarding uncertainty, here’s the latest ECMWF-Ensemble still showing high uncertainty. (Compare to yesterday.)

01-27-26 12 z ECMWF-ENSEMBLE mean sea level pressure standard deviation. (Click on image for a larger view.)

Posted Tuesday 01/27/26 @ 2:06 PM — I wanted to just do a quick update with the latest ECMWF-AI model which just became available. The ECMWF-AI keeps the storm to our east, a marked change from yesterday’s model runs.

01-27-26 12z ECMWF-AI model snow accumulation by Monday morning. The storm only brushes the NJ shore. (Click on image for a larger view.)

One model doesn’t make a forecast in this time horizon of near 120 hours. But I thought I’d post it to counter the NBM model’s suggestion of a possible but uncertain substantial snowfall. Stay tuned!

Sunday Storm Increasingly Possible

Posted Tuesday 01/27/26 @ 12:08 PM — As mentioned yesterday, there is much uncertainty regarding the forward speed and track of a Miller Type A Nor’easter expected to approach our area on Sunday morning. That said, additional models runs since my last posting (00z, 06z and 12z) increasingly show the storm to affect our area. The latest GFS model which just became available shows the storm hugging the coast to our south and then moving northeastward.

The latest Hybrid AI- GEFS (HGEFS) is showing significant uncertainty in the track of the storm, with a strong signal towards a westward track.

01-27-26 06z HGEFS pressure with standard deviation (uncertainty) at 7 AM Sunday. (Click on image for a larger view.)

Even with the above uncertainty, the HGEFS shows 3-5 inches of snow in our area by Sunday evening.

Several other models are also showing a similar 3-5 inches of snow at this time. Based on the trends, I expect it to run much higher, but it’s too soon to be really be sure.

It’s way too early to post snow total possibilities but here’s the latest NBM 13z MEAN snow accumulation forecast for Sunday!

01-27-26 13z Mean Total Snow Accum by 7 PM Sunday. The fine line contours are labeled in 1″ increments (Click on image for a larger view.)

The totals above will likely change in either direction.

There’s incredible uncertainty reflected in the models that comprise the NBM. The MEDIAN snow shows nothing for us!

01-27-26 13z NBM MEDIAN Snow totals (Click on image for a larger view.)

Rule of statistics: When the Median and the Mean are so different, there’s extreme uncertainty.

Stay tuned.

Another Snow Storm?

Posted Monday 01/26/26 @ 4:36 PM — Many of us probably just got done clearing snow after yesterday’s storm and hoping that would be end of it for this winter season. We may be in for another storm this coming Sunday.

The models started showing this possibility two days ago but several had vacillated back and forth with the track. Today’s models are moving towards forecasting a major Miller Type A nor’easter beginning early next Sunday. (Miller classified nor’easters into type A and B based on their origin. This storm originates in the Gulf of Mexico and takes form off the South Carolina coast.

The latest Canadian GDPS with “AI Spectral Nudging” illustrates the path of this storm, a typical Miller Type A—

01-26-26 12z Canadian GDPS with “AI Spectral Nudging” shows a monster Nor’easter early Sunday morning. (Click on image for a larger view.)

There is still uncertainty about the track and its closeness to our area.

Here’s the latest Hybrid AI GEFS (HGEFS) —

01-26-26 12z HGEFS at 1 PM Sunday (Click on image for a larger view.)

Here’s the latest ECMWF-AI—

01-26-26 12z ECMWF-AI forecast for 1 PM Sunday (Click on image for a larger view.)

The AI models have Philadelphia on the western fringe, but with heavy snow in NJ. If it happens, this will be an all-snow event.

It’s too soon to be concerned about this storm. The latest ECMWF-Ensemble (statistical) shows extreme uncertainty in its forward speed and path—

01-26-26 12z ECMWF-ENSEMBLE Sea level pressure uncertainty. This is as high as it typically gets. It suggests it might arrive sooner and or be closer to the coast or be further east. (Click on image for a larger view.)

Originally Posted Mon 10:47 AM — A cold week in store for us.

I’m already getting requests for comment on a major storm for next weekend. As of this morning, only the European AI and regular ECMWF were showing it affecting us. The GFS, GEFS, AIGFS, HGEFS, NAEFS, Canadian GDPS-AI and the German ICON have it moving east of us, not affecting us.

Unlike this past storm, where the models were more in-sync in this lead time frame, there are too many ‘votes’ at this time showing next week’s storm missing us. I’ll be updating later this afternoon with some new model runs. Stay tuned.

I’ve put some updated review information on the last storm’s posting.