Category Archives: Weather Updates


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Mon 11:40 AM Update: This morning’s other models (WRF-NMM, WRF-ARW and the GFS) all show barely a coating to a fraction of an inch of snow accumulating by the end of this storm around midnight in the immediate PHL area and adjacent counties.  The HIREF shows a stronger snow shower possible about 6 PM, not substantially adding to the total.

As I mentioned last night, the new GFS probably did the best with this storm overall.   The much-touted European ECMWF seems to have over-forecast the snowfall here.  

…from earlier this morning—

I was able to review the latest NAM, NAM-NEST and RAP.  All are consistent with the coating to an inch for Philadelphia and surrounding counties.   Below is the NAM snow depth forecast for late this evening—

NAM Snow Depth forecast (in inches) for midnight Monday.  (click for larger image) Most areas much less than an inch around here.

I don’t anticipate any more changes.


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Added Snow Total Forecast Graphics:

GFS Snow Depth
NAM Snow Depth Forecast
ECMWF Snow Depth

Yes, it’s snowing out and that was expected. The forecast question I’ve been trying to address— what level accumulating snow can we expect by the end of this storm?

Last night’s 1 AM run of the models continue with the forecast of a coating to an inch of snow accumulation for our area.  That’s true of the NAM, GFS and high resolution Canadian.  The most recent hourly HRRR  (High Resolution Rapid Refresh) also maintains a low accumulation by the end of the storm this evening.

The only exception is the ECMWF, which has changed from its last run, but still gives us 2 inches with a rapid gradient increase to our north.

It sure looks like snow will accumulate and the intensity is much more than the NAM or GFS forecast QPF values.

Let’s see how it plays out.  Could all these models be wrong??  Could the Eagles lose to Miami??    Stay tuned.

The next models become available later this morning (NAM about 9:30 and the GFS about 10:38 AM) I’ll update if I can.


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10:55 Updated with the latest GFS snow depth forecast—

GFS model snow depth forecast

Well, this forecast has been a roller coaster regarding snow accumulations.

Tonight, I’ve reviewed the latest NAM, RAP, HRRR, SREF,  and WRF models.

Snow lovers will be disappointed.

Basically, the QPF ( quantity of water falling) has reverted to a few hundredths of an inch.  Temps remain just above freezing.  So, little or no accumulation ( a coating) now is the best guess in the immediate PHL area and adjacent counties.


Tonight’s NAM snow depth forecast for Monday.

Here’s another insight.  The new GFS model looks like it was the most consistent and accurate regarding this storm.

We will see light snow tomorrow, perhaps as early as the morning, but just a coating is the best accumulation forecast at this time.

The GFS data becomes available at 10:38 pm. I’ll update if things change.


Last night’s model runs have provided some much-needed clarity to the forecast for late Saturday into Monday.  Each model has previously gone through a series of forecasts which were in poor agreement with each other; last night’s model forecasts are in better agreement and perhaps closer to the likely reality.

Let’s cut to the chase — it appears that recent GFS and prior ECMWF model snow forecasts were very overdone.

A secondary low will form off the NJ coastline late Sunday and move northeastward, not lingering as previously forecast.  The more northern development of this coastal low will keep us in the warmer sector of the storm. Rain on Sunday will likely not change to accumulating snow, only a few snow flurries on Monday.  There’s still a chance that the precip starts as light snow before daybreak Sunday, but quickly changes to rain.

Additionally, it appears that precipitation will be slower to arrive.  Saturday should be dry for much of the day and evening. 

We’ll see if further model forecast changes occur. Stay tuned.