Category Archives: Philadelphia Area Weather Forecasts


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Monday Forecast Update

Update Sun 05/28 @ 6:19 PM— Some cloudiness moved in today as expected and Monday will be similar with high clouds from the city northward and some thicker mid-level cloudiness in areas south of the city.

The Jersey shore will be chilly with an easterly wind flow and significant cloudiness from Atlantic City southward. Some sprinkles possible around Cape May and Delaware.

High Temperatures Monday—

NBM High Temperatures Monday. (Click on image for larger view.)

Looking ahead, another Omega block takes hold over the coming weekend. No rain expected until June 7th!

Update Sun 05/28 @ 7:18 AM — We may see some periods of clouds from the city and southward today along with periods of sun. Northward of the city, things look good. The Jersey Shore will see cooler temps from an easterly wind and some light showers can’t be ruled out in far southern areas (Cape May) and Delaware later in the day. I’ll update later today.

Previously Posted Fri 3:11 PM —

There haven’t been any postings this past week because I’ve been away, but I’ve been keeping an eye on the models and the local weather remotely.

We remain in a very dry pattern with a stalled upper low in the southeastern US and a persistent upper ridge and surface high pressure system blocking any rain from moving into the Philadelphia area from the south. This will continue over the weekend.

The latest NAEFS model forecast for Sunday shows this setup—

NAEFS forecast for Sunday morning. (Click on image for larger view.)

This very dry pattern is a bit of a concern, with our still being in May. Our springtime weather is often much wetter. Hopefully things change; if not, I see the likelihood of parched lawns and stressed trees this summer, as we had last summer. Possibly worse.

Anyhow, it may be premature to worry about a “pattern” with just three weeks of minimal rainfall. I guess we’ll see.

The forecast for this weekend is straightforward, provided the system to our south remains to our south. More uncertainty for Monday.


Sunny with high thin cirrus cloudiness at times as some moisture from the south tries unsuccessfully to move northward.

High temperature 76.7º sd 1.4.º ( NBM model location Blue Bell, PA)


Sunny but a bit more cloudiness southern areas, especially late in the day. Moisture from the south still trying to move northward will cause the cloudiness towards Delaware and South Jersey.

High temperature 78.8º sd 1.8º ( NBM model location Blue Bell, PA)

Monday – Memorial Day

Sticking with the NBM model, some cloudiness just north of the city, becoming sunny in the afternoon. Cloudy in areas south of the city, especially South Jersey and Delaware. Some very light sprinkles are possible in the same areas.

NBM clouds forecast 1PM Monday. Clouds recede partially southward during the afternoon. ( Click on image for larger view.)

High temperature 81.5º sd 2.1º ( NBM model location Blue Bell, PA)


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Update Fri 5/19 4:05 PM — This afternoon’s models suggest a heavier band of rain may develop directly over Philadelphia. That would be a significant change in the forecast of the past several days.

Previously Posted Fri 9:45 AM —

A coastal system will brush the Philadelphia area with light showers as it moves northeastward early Saturday morning.

A cold front approaches from the west during the day Saturday and moves through early Saturday evening with showers and possibly a few thundershowers. Most of the energy and rain will move up to our west missing us.

The models are in general agreement that the immediate PHL area and some areas to our immediate west likely will miss out in some much-needed rain—

HREF model forecast for total precipitation for Saturday. (Click on image for a larger view.)

Following the cold front, we’ll re-emerge into the same general pattern of a cooler and dry weather pattern—

NAEFS forecast for Monday shows pretty much the same pattern we’ve been in: a cool trough pattern over the northeastern US and a warm ridge over the west.


Clouds and showers in the morning, mainly from the city and east into NJ. Becoming sunny thought high cirrus clouds for much of the day. Clouds roll in later afternoon with some light showers in the evening. Many places from the city and immediately westward may not see any showers.

High temperature74.4º sd 2.9º ( NBM model location Blue Bell, PA)


Sunny. Breezy

High temperature 77.7º sd 2.0º ( NBM model location Blue Bell, PA


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Saturday Forecast Update

Update Sat 05/13 @ 10:58 AM — Here’s what we have at 11 AM

Current 11AM MRMS radar and RAP data. (Click on image for a larger view.)

This is last night’s NBM (not previously posted)—

Last night’s 00z NBM (available at 9:30 PM EDT) showing the extent of the light showers. (Click on image for a larger view.)

Update Sat 5/13 8:12 AM — I knew my ‘dry’ forecast was a low confidence forecast. A few sprinkles have fallen this morning. Last night’s HRRR and Canadian maintain a dry forecast as shown in last night’s graphic.

Last night’s 00z NAM-NEST also showed a dry forecast, but its 06z run shows light sprinkles from the city southward, especially in the early afternoon.

It should be noted that NOAA- NWS is working on a next generation model, called the RRFS (Rapid Refresh Forecast System), scheduled for release sometime this fall. It will actually replace several models: the NAM-NEST, HRRR, HIRESW-ARW (all three versions) .

While not ready yet for prime time, here’s its current forecast compared to the HRRR:

Pre-release beta version of the RRFS. It shows more more shower activity north of the city (blue) than the current HRRR (red) at 2 PM. (Click on image for larger view)

Anyhow, I’m going to backtrack on my ‘update’ from last night and removed the strike-out from the forecast posted below to its original form.

Saturday Forecast Update

Update Fri 05/12 @ 9:58 PM — It hasn’t been even an hour since I posted this Weekend Weather Forecast, but I’m going to remove the mention of showers in the immediate PHL area for Saturday, based on the latest HRRR just becoming available and the consistent forecast of the Canadian models.

So I’m going to call for no rain here, despite the GFS, NBM and ensemble forecasts to the contrary.

Tonight’s 00z HRRR shows most of the immediate PHL area dry on Saturday. (Click on image for a larger view.)

Previously Posted Fri 9:23 PM —

A disturbance is expected to move to our south on Saturday with the rain shield staying in Maryland and southern Delaware. As has been the case over the past few days, some models keep the immediate PHL area dry.

However, at this point there are enough models, particularly the statical ensemble models, forecasting very light scattered showers moving through Montgomery county and into New Jersey, that I need to include that possibility in Saturday’s forecast. I’m not all that sure about this aspect of the Saturday forecast because the Canadian models have consistently kept us dry.


Cloudy with very light and scattered showers as early as 8 AM. Heaviest showers (if they occur here) early to mid afternoon.

High temperature 78.4º with a high uncertainty as expressed as a higher than normal standard deviation of 4.4° ( NBM model location Blue Bell, PA)


Some cloudiness early morning, becoming sunny by late morning.

High temperature 72.5º sd 1.5º ( NBM model location Blue Bell, PA)