High pressure will gradually move off to the northeast over this weekend.
On Saturday, it will be mostly sunny in the morning. A flow of milder air will move in aloft on Saturday afternoon, causing some mid-level cloudiness during the afternoon hours. High temperatures 58-60. It will still be breezy.
Still cold Saturday night with lows in the mid 30s.
Sunday will be mostly sunny and milder. High temperatures 61-63.
Forecast Update: Sunday will be sunny and milder. High temperatures 65-67
The southwesterly flow of above average temperatures will be with us on Saturday, with mostly sunny skies and temperature highs of 83-85..
Some cloudiness moves in late Saturday afternoon as a cold front drops down from the north.
Winds become easterly Saturday night and clouds and scattered light showers with drizzle are possible Sunday morning although the heavier rains don’t move in until later in the afternoon on Sunday.
There remains uncertainty about high temperatures on Sunday. The Model Output statistics have highs around 58, but the experimental models continue to show a wide range with highs likely being much cooler. (48-50 is possible) It becomes windy during the day.
Heavy rains and windy Sunday night into early Monday morning.
The models continue with the scenario of low pressure moving along a stalled frontal boundary.
Reviewing today’s NAM and GFS data, the rain-snow critical thickness cuts right through Philadelphia. QPF values are about 0.39 inches water.
Additionally, until precipitation gets going, it will take some time for dynamic cooling to establish a cold enough profile. However the middle levels of the atmosphere will remain too warm for snow to form in much of Philadelphia, south and east.
For most of Philadelphia, rain may mix with some sleet and maybe some rain snow mix after 4 AM, but should barely accumulate, even on grassy surfaces. It should be wet, not white, in most of Philadelphia.
Precipitation ends about 9 -10 AM.
For extreme Northeast Philadelphia, Chestnut Hill and areas of Montgomery County and Bucks County, 1/2 to 2 inches measured on grassy surfaces is possible, but even less on roadways. The graphics below best depicts this snow accumulation potential—
Much of South Jersey will have no accumulation. Temperatures rise in the morning and rapid melting will occur with whatever falls.