Category Archives: Weather Updates


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No showers developed Philadelphia and west, as expected. There were some thundershowers in south Jersey, not as much areal coverage as predicted by the models last night. Dew points were delightfully lower than had been predicted.  

Pop-up, widely scattered thundershowers did develop today (Saturday), but the areal coverage was hardly close to the model precipitation forecast graphics that I posted yesterday. (This morning’s models which came out after 10:45 am had actually cut back on the showers for today.)

Tonight’s model forecast just becoming available shows even fewer showers for the immediate Philadelphia area westward, but a weak frontal boundary passing through sparks some thundershowers, mostly from the city eastward into N.J. mid to late afternoon.

Current WRF 1hour accumulated rain forecast Sunday 4:30 pm

As we’ve seen today, prediction of specific areal location of thundershowers is something models attempt to do with limited and inconsistent success.

Except for these showers, Sunday will be mostly sunny, very warm and somewhat humid— typical August weather. High 87-89.



There are interesting differences in last night’s models regarding the chance of showers/thundershowers this evening. (Sunday evening)

An upper air disturbance drops down into our area this evening, between 7PM and 1 AM.  The NAM has been consistent in keeping any showers far to our north.  One version of the WRF with NAM physics (WRF-NMMB) also does the same.

The GFS  (and its similar physics version, the WRF-ARW) has showers and thundershowers making it in to the Philadelphia area towards midnight, then dissipating.   It will be interesting to see which model does the best here.

Either way, today will be hot and slightly more humid. Highs 91-93 with dew points near 60.


Today’s official high temperature was 97 and the high heat index was 106.

The global GFS overshot the temperature forecast. The mesoscale models (NAM, WRF, HIREF) did better with the temperatures but over-forecast the pop-up showers in a big way.

Tonight’s models, just becoming available, are predicting a hotter day on Sunday than Saturday. Highs are coming in at 98-100. Thunderstorms move in from the northwest after 8PM Sunday evening.

Sunday Weather Update

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Some cloudiness did develop mid afternoon, especially north of the city. But, it really wasn’t worth focusing on…essentially, this was a beautiful, sunny day.

The most recent NAM and WRF models continue to show upper air disturbances rotating through our area early to mid afternoon from an upper cyclonic flow around a closed upper low off northern New England. (The GFS does not have it this far south.)

Areas of upward vertical motion (pink-blue-magenta) and vorticity (yellow lines) at 2:30 PM today

Some cloudiness is expected about 1-4 PM from this disturbance. Widely scattered sprinkles also possible, especially far north. Skies clear out later afternoon.   High today 85-87.

So without the GFS on-board with this forecast, we’ll see how the WRF does.