Philadelphia Area Weather Forecasts

THIS WEEK’S WEATHER

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Friday Forecast Update- A New Wrinkle

Posted Friday 12/05/25 @ 9:05 AM — Current Radar and Water Vapor imagery shows the snow falling to our south. Unless there is strengthening of the southern system expanding it northward, it looks unlikely that the precipitation shield will over-spread the area as forecast by last night’s REFS. Yesterday’s NBM forecast looks to be the ‘winner’. Flurries, at most, can be expected near the city.

Current Radar Water Vapor—

This morning’s Water Vapor with superimposed KDIX radar and MRMS radar. RAP model 700 mb winds and Omega shown. Green Arrows— Upstream from us, there is no precipitation failing. (Click on image for a larger view.)

Here’s the latest 12z NBM, just available—

Today’s 12z NBM Total Snow accumulation; It shows no snow accumulation even close to Philadelphia. (Click on image for a larger view.)

We’ll stay with the NBM with this system. As the storm moves off the coast, some moisture and warm air will be thrown back into our area. Some freezing rain/drizzle is expected after midnight.

12z NBM shows light drizzle and freezing rain and a mix moving in from the southeast after midnight. (Click on image for a larger view.)

I’ll update later this afternoon with this new wrinkle in the forecast.

Friday’s “Minimal Snow” Update

Posted Thursday 12/04/25 @ 7:24 PM — The latest ECMWF-AI, REFS, and Canadian AI models are showing a bit more snow, but it still comes down to only a dusting to a coating— much less than 3/4″. Here’s the REFS model forecast—

18z REFS forecast total snowfall for Friday. Contours are labeled (Click on image for a larger view.)

Interestingly, the REFS forecast has changed the timing from the earlier posted NBM, with light snow moving up from the south about 10 AM and taping off significantly during the early afternoon. Not much additional after 2 PM.

Friday’s “Minimal Snow” Outlook Update

Posted Thursday 12/04/25 @ 11:32 AM — A quick update on the “minimal snow” forecast by some of the models for Friday afternoon.

This “snow” was always a low probability forecast, especially when predicted accumulation is in the coating to dusting range.

The Model Blend (NBM) statistically combines the forecasts of 30-40 different models, statistically weighting each constituent model’s forecast through a comparison of how each performed over the prior 6 hours compared to the actual conditions (as captured in the 6 hour delayed URMA model). It also weights each model based on historical accuracy.

The latest Model Blend (NBM) shows almost no snow in its statistical outputs.

Here’s the mean (average) snow predicted—

15z NBM mean snowfall by late Friday evening. This is consistent with the experimental RRFS and REFS model forecasts. (Click on image for a larger view.)

Here’s the 75 percentile accumulation total. The 75 percentile means that 75 percent of the 30-40 models are forecasting at or below this amount—

15z NBM 75 percentile. (Click on image for a larger view.)

It should be noted that the low resolution ECMWF-AI still is forecasting a coating, especially for South Jersey.


This amount of snow for us doesn’t really merit the time put into it, but I’m staying in practice for later season snow events.

Thursday Update

Posted Thursday 12/04/25 @ 9:02 AM — As forecast by the REFS yesterday, a line of very light snow flurries/snow showers is expected to move through about 10 AM. It’s currently visible on radar, although much is not reaching the ground. See caption for more info—

Radar with visible Satellite superimposed at 9 AM. Much of these echoes are not reaching the ground. The superimposed RAP model Omega shows moderately strong upward motion over Philadelphia, suggesting an increase in intensity as it moves over the city into NJ. It’s then expected to dissipate. (Click on image for a larger view.)

The rest of the forecast remains on track for Thursday, as does the snow outlook for Friday.

Thursday: Cold to Colder

Posted Wednesday 12/03/25 @ 5:17 PM — This late autumn season is much different than recent previous years. It wasn’t too many years ago that I still had some hardy flowers on our deck hanging on for dear life in early December and I can remember recent years where temperatures repeatedly reached the mid 60s until the last week of December.

Thursday will likely dispel any hopes of similar warm ups in the near term. A strong cold front approaches with an increase in clouds during the morning.

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 current air mass is dry and there isn’t much moisture to wring out in the form of showers with this front. A latest REFS ensemble member shows some light snow showers moving through Thursday morning about 10AM, just ahead of the front with some dark clouds.

The actual front moves through early afternoon with another reinforcing shot of cold air towards evening as winds pick up. Partly cloudy skies the rest of Thursday afternoon.

Friday will be cold. High temperatures on Friday may not get above 32º with wind chill temps in the mid 20s at best.

Over the past week, I’ve been watching a storm for later Friday that most, but not all, models have the snow associated with it suppressed to our south. The few models that show light snow reaching our area only crank out about 0.5″ of snow at most- a dusting or a coating. I’m watching this system and will continue to update.

After reminiscing about warmer Decembers earlier, I’m reminded that some very cold Thanksgivings and early Decembers gave way to very mild Februaries . Current cold conditions don’t necessarily portend a very cold winter.

Wednesday through Friday

Posted Tuesday 12/02/25 @ 7:20 PM — Skies clear for Wednesday. There should be plenty of sunshine and while instability cloudiness sometimes develops with an exiting storm, the models don’t show this for Wednesday.

Thursday, a strong cold front moves through mid day with just clouds at this time. Winds pick up quite a bit towards evening as temperatures plummet.

Very cold Friday, with highs in the low to mid 30s! For Friday, another coastal system is expected to move up the coast, but slide just to our south. Most models have the precipiation of this storm totally missing our area, but the ECMWF-AI model has consistently showed some light snow falling by Friday evening.

This afternoon’s German ICON model has joined the ECMWF-AI with a forecast of a dusting to a 1/2 inch coating by Saturday morning. But our GFS model and the Canadian GDPS-AI version have the precipitation passing us to our south, as does the current RRFS.

I’ll keep an eye on it.

Today’s 18z ECMWF-AI forecast for 7 PM Friday evening. Based on thickness levels and temperatures, any precipitation that falls north of the red line will be snow. (Click on image for a larger view.)
Tuesday Mix-> Rain Update

Posted Tuesday 12/02/25 @ 8:24 AM — The precipitation began as early as 6:45 AM -7 AM in our area as forecast and there was/is some ice pellets mixed in closer to/in the city.

Here’s the current MRMS “hydrometeor” scan showing various forms of precipitation —

MRMS Hydrometeor classification at 8:12 AM Hydrometeors is a catchall fancy name for ANY FORM of precipitation. For the MRMS, here’s the code meanings: BI: Biological scatterers (birds/insects) GC: Ground Clutter IC: Ice Crystals DS: Dry Snow WS: Wet Snow RA: Rain (light/moderate) HR: Heavy Rain BD: Big Drops GR: Graupel HA: Hail (often mixed with rain, noted as RH) UK: Unknown

For most of the area, this changes to all rain. The latest models show the rain ending from west to east as early as 2:30 PM to 4 PM.

Late Forecast Update

Posted Monday 12/01/25 @ 9:00 PM — Temperatures around the city have dropped below freezing (expected). The latest 00z models (HRRR NBM) are still painting a similar forecast.

But, inspection of the vertical thermal profile of the latest HRRR suggests that the early period, 7AM-9AM, may have more icy conditions or sleet closer to the city than the model precipitation type has been showing. (The models are still saying rain near the city.)

Some ground surface temperatures may be still cold enough for freezing and temperatures aloft at critical levels are still below freezing in our area at 9 AM. Snow isn’t likely, but ice pellets or some rain ice mix is. Here’s what I’m talking about—

00z HRRR with simulated radar and critical vertical level temperatures that are still below freezing at 9 AM (Click on image for a larger view.)

Just a possibility. Sometimes the model precipitation types are wrong.

Rainy Tuesday Update

Posted Monday 12/01/25 @ 4:48 PM — No significant changes in the forecast posted this morning. Here are some additional points—

  • Rain or Snow (depending upon location, see animated gif below) begins between 6 AM and 7 AM
  • Changes to all rain by late morning in most of our forecast area.
  • Little to no final accumulation in Upper Montco, Bucks, and Chester counties— areas where it had snowed.
  • Rain ends from southwest to northeast around 3-5 PM
  • Some sun breaks out in western areas before sunset.
  • Winds increase and become quite gusty towards evening.
RRFS Conditional Precipitation Type- (Snow sleet Freezing rain) 7 AM 8 AM 10 AM (Click on image for a larger view.)
Tuesday Forecast Update

Posted Monday 12/01/25 @ 9:49 AM — Last night’s models along with the early morning models continue with these trends for Tuesday’s storm. Here are the current trends—

  • Precipitation begins as light rain or light snow (north west) as early as 6 AM. Virtually no snow in NJ, in Philadelphia and immediate locales north and west.
  • Snow north and west likely changing to rain.
  • Far northwestern suburbs may have a period of freezing rain.
  • Transition to rain by late morning.
  • Heaviest rainfall in NJ.
  • No changeover back to snow expected at the end early Tuesday evening.
  • Windy early Tuesday evening.

At 8 AM most of the area will be rain—

Latest 13z NBM with precipitation type and surface temps at 8 AM. (Click on image for a larger view.)

Total Snowfall Accumulation (Model Blend, also supported by RRFS forecast)—

13z NBM (model blend) snow accumulation. (Click on image for a larger view.)

Total Precipitation (water and snow-water equivalent)

13z NBM total water precipitation (Click on image for a larger view.)
Stormy Tuesday

Updated Sunday 11:15 PM — The trend with tonight’s models is for little to no accumulation except in north and west Montco Bucks and Chester counties. It appears there will be no changeover from rain to snow towards the end of the storm. The heaviest precipitation (rain) will be in NJ. Updates tomorrow.

Originally Posted Sun 5:10 PM — This week will see the approach of a winter-like coastal storm at a time when we are still in astronomical Autumn.

Following a sunny but unseasonably cold Monday (high low 40s), clouds will increase around sunset Monday. Low pressure developing near the Gulf of Mexico (America) Mexico will lift northeastward towards our area.

12z ECMWF-AI model forecast for 7 AM Tuesday morning. The red , yellow and magenta contour lines are “critical thickness lines” which is a rough way of determining rain, sleet and snow. North of the red line (500 mb-1000mb), the atmosphere is generally cold enough for snow. North of the magenta (700-850 mb) and/or yellow (850-1000 mb) lines, the atmosphere is cold enough for sleet and/or freezing rain. The white line is the near ground level 32º freezing line.

Precipitation may start as light snow near or north and west of the city, but is expected to quickly change to rain. Northwest of the city, (Berks county, Lehigh county) the precipitation may mix with rain or stay mostly snow.

Staying with the AI model and zooming in at 7 PM, the atmosphere (based on the thickness lines) has chilled down to support some snow just north and west of the city just as the precip is raining. Note the the 32º freezing line is still far northwest, so not much of any snow is expected to accumulate on wet ground. But there’s some uncertainty.

12z ECMWF-AI model forecast for Tuesday 7 PM. Still some precip falling and the critical thickness lines are closer to the city. (Click on image for a larger view.)

So mostly rain, heavy at times, after some light snow in the morning, possibly changing back to light snow with light accumulations possible early Tuesday evening.

There’s fairly good model agreement with the track of this storm and the been good continuity between model runs.

In winter with an overall colder atmosphere, the would be a major snow storm for us. However, it’s early in the season and perhaps this year will be like last year, where there had been “not enough cold air” for major snowfalls here.

Total precipitation or snow-water equivalent will be fairly high, 1-1.3″ water.

Things to watch—

  • If the precipitation comes in early, much before daybreak (as some models are showing), we may have more snow accumulation before the changeover to rain.
  • High precipitation rates early in the storm may cause dynamic cooling, bringing temperatures near the surface closer to freezing.
  • Cold air may rush in after the main low passes, either drying things out or causing a burst of snow.

Food for thought

If the immediate PHL area will have any snow accumulation, it will occur towards the end of the storm. This is low confidence, but still a possibility.


Here’s the Model Blend forecast snowfall —

18z NBM forecast snowfall by 10 PM Tuesday evening. (end of storm) (Click on image for a larger view.)

Here’s the latest GFS forecast, just available—

18z GFS forecast for midnight Tuesday. (Click on image for a larger view.)

The latest RRFS and REFS not yet available, but the 12z RRFS was leaning towards much lower snowfall totals

An interesting early winter storm. Stay tuned for updates.