WEEKEND WEATHER FORECAST

High pressure will control our weather this weekend. Sunny skies and low dew points will provide a welcome change from most of this summer’s past weekends.

Highs on Saturday 81 and Sunday 85.

As the high moves east, it will merge with a Bermuda high giving us a hot southwesterly flow for next week. The chance of rain for the next six days is very low.

WEATHER UPDATE

Latest NAM maintains mostly cloudy conditions for Sunday.  A northeasterly flow will bring cool conditions with highs in the mid 70s. Areas in NJ may have lingering showers.

9AM Sunday Update: I was surprised to wake up to widespread showers.  Current radar has showers extending as far west as Reading. While lingering showers had been expected in NJ, this coverage of precipitation was not forecast for PHL and west.  The latest short range models (HRRR, NBM-H) now have showers lingering until about 2-3 PM in PHL!

I can’t remember a time in the past where the model forecasts have repeatedly been so far off in the short range.  

2 PM Sunday: Yet another update: The latest NBM-H has the showers lingering through the rest of the afternoon!  Looking back to my Friday forecast, the GFS did better for Sunday’s forecast of showers all day. 

WEEKEND WEATHER FORECAST

A large area of weak low pressure will move up northeastward into New England tonight as its associated front lingers back across our region tonight through Saturday night.

Showers and thunderstorms are expected this evening (Friday), although the heaviest dynamics will pass to by to our west and north.

Fri 10pm update: The thunderstorms went with the dynamics Friday evening and remained west and north of Philadelphia. With the near range forecast so far off, it suggests that the models, especially the GFS, may not be handling the stalling front very well this weekend.  The forecast below for Saturday was based mostly on the NAM and it appears to be on track for mostly dry conditions before 3 pm Saturday. 

On Saturday, the lingering frontal boundary remains through Pennsylvania and into West Virginia. This will allow low pressure to develop along the frontal boundary in Maryland as it sags to our south later on Saturday afternoon and evening.

Saturday may have some brief scattered showers in the mid-morning, but much of the day before 3 PM will dry. With a mix of clouds and some sunshine, high temperatures may reach 86.  It will be humid.

With the low developing on the front to our southwest, there will be an increasing chance of showers and thunderstorms after 3 PM into Saturday evening.

The showers may linger into early Sunday morning, but as the low pressure moves off the Delaware coast, drier air should move in during the day on Sunday, according to the NAM.  However,  the GFS maintains a chance of showers throughout the day on Sunday.  I’ve been mislead by the NAM on recent past weekends, but we’ll see what happens.  Sunday may remain mostly cloudy with some brightening skies later in the day.  Highs near 81 with lower humidity

I’ll likely update again late Saturday.

WEEKEND WEATHER UPDATE

Upper air low pressure remains near the area for Sunday.

After some slow clearing in the morning, there should be periods of sunshine in the morning and early afternoon.

Instability with abundant moisture and some heating from sunshine will allow for showers and thundershowers to develop late afternoon into Sunday evening.

While a widely scattered shower can’t be ruled out, much of the day before 3 pm should be dry.

More showers and thundershowers should develop between 3 and 7 pm, although the intensity is not expected to be as great as Saturday’s storms.