Philadelphia Area Weather Forecasts

WEEKEND WEATHER FORECAST

Update Sat @ 5:07 PM — Sunday’s forecast (below) remains on track with clearing from west to east between 10 AM and about noon. Colder, more seasonable temperatures on the way.

Next week has a flat jet flow (shown below) with little chance of any snow here in the Philadelphia area for Christmas.

No major weather events currently predicted for us, although there are some significant differences emerging in the long range ensemble models that may throw some spice into an otherwise straightforward outlook.

Update Fri @ 10:50 PM — Tonight’s models have the rain lingering until late morning. Then dark low clouds, but there’s the possibility of drizzle, fog and mist continuing. A memorably gloomy day with the low sun angle behind a thick, low cloud deck.

The sun returns by late morning Sunday.

Update Fri @ 5:55 PM — This afternoon’s models show little change in the forecast below. Saturday forecast changes are highlighted below.

Previously Posted Fri 10:20 AM —

This early edition forecast will be updated Friday evening.

A blocked pattern with a split jet stream has affected our area and has given us the mild weather this past week, as described in the graphic caption below—

Jet Stream forecast for Sunday 10 PM. (300 mb wind speed). Blocked pattern due to major ‘kink’ (1) in the jet flow over Pacific has caused the upper scale ridge (2) to be with us for most of this past week. This ridge (2) will finally move offshore by Sunday evening, allowing more seasonably cold air to move in. However, the jet flow will be split between two streams, causing long range forecast uncertainty next week. A flat component to the jet (3) will move in for much of next week, but the southern jet may create some interesting weather.

For this weekend, a cold front will move through as the above mentioned upper ridge (2) moves east into the Atlantic.

Saturday

A departing high pressure system will bring an easterly damp, colder flow ahead of an approaching cold front. Most of the showers will move through early Saturday morning and be north of us by 9-10 AM.

The remainder of the day, dark low-level cloudiness and damp with a chilly easterly wind. Some fog and haze also expected. Showers return during the evening and after midnight ahead of the actual cold front. High temp 47.4º ± 3.0º NBM model Blue Bell.

Sunday

The front slowly moves through after midnight Saturday and Sunday will start cloudy, but clouds should break for sunshine about 10-11 AM. Somewhat windy. High temp 42.7º ± 2.1º NBM model, Blue Bell.

Winds
NBM Wind forecast Blue Bell PA