Philadelphia Area Weather Forecasts

WEEKEND WEATHER FORECAST

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Saturday Update

Posted Saturday 05/24/25 @ 9:37 AM — Last night’s forecast still holds. The sunshine this morning will be mixing with clouds by about noon. There’s a chance of an isolated, fast moving light shower about 3-5 PM. although most areas are expected to remain dry.

Current Water Vapor with Radar shows the disturbance expected to move through—

Water Vapor, radar composite and RAP model vertical motion around 9:15 this morning (Click on image for a larger view.)

Previously Posted Fri @ 6:19 PM — —The main low pressure system that affected our weather over previous days is slowly moving away, but the first upper low and a second upper low will bring cool weather and unsettled skies at times through the first portion of the Memorial Day Weekend. Monday should be mostly sunny.

(An upper low can be thought of as a cold circulation of air aloft.)

ECMWF-AI forecast for Sunday at 8AM 1 and 2 are upper low pressure systems. The red lines are called 540 thickness lines, and they demarcate colder average temperatures of the lower half of the atmosphere. In winter, areas north of the 540 thickness lines are cold enough for snow. In late spring, that cold air causes instability to develop with sunshine heating the ground. (Click on image for a larger view.)

We had widely scattered fast moving showers late this afternoon, and with cold air aloft, that possibility still exists for Saturday afternoon. Sunday, any instability showers should remain far north of the Philadelphia area.

It should be noted that any really warm weather isn’t forecast for our area this weekend or even for the coming week.

Saturday Forecast

Sunny in the morning. Instability cloudiness develops before noon and lasts several hours into the afternoon. A few, isolated showers move through at that time. Most areas will be rain-free. It will be windy during the mid-day hours.

NBM high temperatures: Blue Bell, PA 63º Philadelphia, PA 66º
Uncertainty:average (based on standard deviation): ± 1.9º

Sunday Forecast

Partly sunny, although the experimental RRFS shows considerable cloudiness south of the city and in Southern NJ. Less windy but still breezy.

NBM high temperatures: Blue Bell, PA 68º Philadelphia, PA 70º
Uncertainty: average (based on standard deviation): ± 1.8º

Memorial Day

Sunny. Winds subside further but still breezy. High thin cirrus clouds move in late afternoon.

NBM high temperatures: Blue Bell, PA 68 72º Philadelphia, PA 74º
Uncertainty: low (based on standard deviation): ± 1.4º