GFS forecast for Saturday evening
GFS forecast Saturday evening

The outlook for this weekend’s weather is looking remarkably similar to last weekend’s weather.  (Not a good thing!)

Like last weekend, high pressure nosing in from the northeast will result in an easterly wind flow that will keep things damp and cool. Moisture from the remnants of Alberto transported into the Midwest will also be pulled in.  Weak low pressure is also expected to develop near the Delmarva and remain blocked from moving away, also resulting in low clouds and showers/thunderstorms.

Like last weekend, there are differences between the GFS and NAM with the GFS having heavy rain on Sunday, but the NAM not so much.  I think the NAM did best last weekend.

So there’s uncertainty about how much rain and when.   Right now Saturday looks like the wettest day, based on the NAM.  Sunday may turn out drier.


Some additional showers are expected to move in about 6 pm today. Things dry out late tonight.

HRRR Sunday forecast 6 pm

Monday starts cloudy, but expect sunshine by mid morning.  Monday should turn out to be a nice day!  High near 80.

Sunday 8 PM Update -This afternoon’s NAM and GFS model runs maintain low clouds and even some light spits Monday morning, with just clouds in the afternoon.  No sun




Sunday 3 pm Update: Some additional showers are expected to move in about 6 pm today.  Things dry out late tonight.  Monday starts cloudy, but expect sunshine by mid morning.  Monday should turn out to be a nice day!  


Regarding thunderstorms today, the latest HRRR shows widely scattered thunderstorms between 5-6 PM in the Philadelphia area.  The key words are widely scattered.  This is not predicted to be the usual long line of thunderstorms.   The statistical models are more impressive from a probability basis, but many areas may not see anything this afternoon.

widely scattered thunderstorms
HRRR prediction at 5 PM Saturday


The Philadelphia area forecast for this weekend has clarified a bit more.

Saturday will start sunny; high dew points in the 60s and high temperatures in the mid to upper 80s will make it an appropriate start of the summer season.

Unfortunately, moisture will also move in as mid-level cloudiness between 2 and 4pm.  There’s a high chance of showers and thunderstorms between 4 and 6 pm and the showers will likely continue into the evening.

The stream of moisture,  instability and cloudiness  are firmly entrenched by Sunday.  The GFS maintains showers throughout Sunday BUT the NAM holds off most of the precipitation  until later in the afternoon Sunday.  So there’s uncertainty about timing of showers on Sunday. I’m betting on the NAM here at this time. Any showers will be heavy.  High 78.

11pm update: Sunday possibly looking better in the afternoon as a backdoor cold front noses in from the northeast.
High pressure noses in Sunday afternoon 

Monday starts off cloudy, but expect some sun by late in the afternoon.

I’ll try to nail down the timing of the showers with updates.