Category Archives: Weather Forecasts



Updated Sun 11:22 PM — Tonight’s models show thunderstorms of greater intensity as the front moves into New Jersey early afternoon.

Update Sun @ 7:38 PM — Most models show the timing of the front as described below. But, the latest RAP model and GFS have the main wave of the front moving through much earlier. The GFS has showers starting as early as 10-11 AM and the RAP as early as 8-10 AM.

Update Sun @ 5:44 PM — A cold front will move through our area Monday morning through early afternoon with showers and thunderstorms.

The front is likely to come through in two waves— an early period 6-8 AM with very widely scattered showers and storms. Another wave approaches about noon to 2 PM with a more distinct line of showers and thunderstorms. No severe storms expected here. Heavy rainfall (1-1.5 inches) in some locales will be the main impact.

Today’s 18z NAM forecast for 2 PM showing heavier rains (3 hour totals) north of the immediate PHL area as well as southward. Some areas may have 1.5″ rain, some may have less than 1/2 inch. (Click on image for a larger view.)

Since the front is coming through early, daytime heating effects will be minimized. This will reduce the likelihood of any severe weather. The energy with this front is distributed in two waves, also reducing severity. Possibly stronger storms will be nearer the Jersey shore and southward into Delaware.


Updated Sat 10:35 PM — Current Sunday forecast looks good. High temps 90-92°, dew points low 60s. The approaching cold front won’t affect us until Monday morning.

Showers and thundershowers Monday morning and early afternoon with the cold front likely will not be severe in our area. Some areas of heavy rain possible.

The upper air low pressure system will finally move out allowing high pressure and an upper air ridge to move in bringing much warmer conditions, above seasonable average temperatures. (average highs are 83º Blue Bell and 85º Philadelphia)

Today’s 18z GEFS shows the upper ridge (1) the upper low (2) and a cold front moving towards us (3) late Sunday. By the end of the week, the typical Bermuda high pressure (4) will move into its usual position bringing more heat and humidity. (Click on image for a larger view.)

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Sunny and somewhat warmer. Lower dew points in the low 60s. High temperature 90.5º ± 3.5º NBM model, Blue Bell PA.

Today’s 19z NBM Model high temperatures Sunday. Black contours are 2 degree increments. (Click on image for a larger view.)

A cold front moves in late Sunday evening and overnight with showers and thunderstorms into Monday morning.


Updated Sat 7:48 PM — Sunday will be sunny. Still very windy. Wind gusts 30-40 mph. High temp 73.4º ± 1.5º NBM model Blue Bell. (Average seasonal high this time of year is 83-84°)

Update Sat @ 10:25 AM

Forecast Review— Despite the lack of most models’ support, instability cloudiness did develop during Saturday morning. Why the models don’t seem to forecast this very well is a mystery to me, but I’ve seen it happen many times in similar setups.

Increasing sunny breaks and sunshine should begin during the afternoon; I’m basing this on the ICON and ECMWF models which did show this cloudiness.

Updated Fri 11:06 PM — Tonight’s models have backed away from the Saturday morning cloudiness.

Update Fri @ 5:59 PM — Forecast Updated in below

High pressure builds in behind a cold front Friday. We’ll be under the influence of high pressure at the surface and low pressure aloft—

GEFS jet stream wind forecast for Sunday showing low pressure aloft in the northerast. Persistent upper ridge in the Midwest will bring very hot temperatures to that area. We’ll be in the cooler section of the pattern. (Looks like a persistent omega block appearance to me.) Will have to keep an eye on the jet streak in western Pennsylvania. This cold bring some instability cloudiness, although it’s not being forecast. (Click on image for a larger view.)

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Mostly sunny and delightful. High temp 75.0º ± 2.5º NBM model Blue Bell.