The forecast for this weekend has been essentially unchanged for several days. As described earlier this week in This Week’s Weather, the frontal system moving through tonight will transfer its energy to a coastal low in New England. Much of the dynamics that go into precipitation will be lifting away from us and we’ll have very little rain.
The latest forecast from the NBM shows a bit more rainfall tonight than previous forecasts—
Latest NBM model forecast 00z , just available. Accumulated rain tonight (Click on image for a larger view.)
The front comes through tomorrow morning around daybreak with clouds breaking for sunshine by 9-11 AM and winds picking up late morning.
With a strong pressure gradient from the intensifying low pressure off the New England coast, our winds will be the big story on Saturday and to some extent Sunday.
NBM Wind Meteogram for location Blue Bell, PA (Click on image for a larger view.)
As mentioned last night, I’ve begun playing with the RRFS model still under development. Here’s its wind forecast for the weekend—
Today’s 18z RRFS wind forecast for Blue Bell PA. Somewhat more windy the forecast by the NBM. (Click on image for a larger view.)
Saturday
Cloudy early, then sunshine breaks out about 9-11 AM, earlier far west. Windy. High Temperatures will occur about noon, then decline
High temperature 55º ( NBM model— location Blue Bell, PA) High temperature 57º ( NBM model— location Philadelphia, PA) Uncertainty ± 1.7º which is average.
Sunday
Sunny and still somewhat windy. For the start of the Philadelphia Marathon 37º at 7 AM. By 10 AM 47º Still windy with gusts to about 18 MPH by 11 AM.
High temperature 53º ( NBM model— location Blue Bell, PA) High temperature 55º ( NBM model— location Philadelphia, PA) Uncertainty ± 1.3º which is higher confidence.
A large storm expected Tuesday through much of Wednesday with rainfall about 1.3″ in much of the area.
The axis of rain was further north than had been forecast by many models yesterday. The Canadian HRDPS was an outlier and offered the correct forecast, somewhat followed by the GFS and ECMWF.
As mentioned, the upper air pattern for the weekend as forecast several days ago has become less amplified in the Northeastern US. It will still get colder, but not as cold as previously thought.
Here’s the latest NAEFS forecast for Sunday, showing a high pressure ridge with two centers that will bring cold but fair weather to us—
Today’s 12z NAEFS shows to centers of high pressure keeping clear skies over us. Low pressure off the SE coast will stay well to our south. The 540 thickness line (red contour) will be right over us. In winter, this is often the general dividing line between rain and snow, neither will we be seeing. (Click on image for a larger view.)
Saturday
Sunny and colder. Breezy, especially mid day.
High temperature 53º ( NBM model— location Blue Bell, PA) High temperature 55º ( NBM model— location Philadelphia, PA) uncertainty-low; sd of about ± 1.3º
Sunday
Continued sunny and cold. Light winds.
High temperature 48º ( NBM model— location Blue Bell, PA) High temperature 50º ( NBM model— location Philadelphia, PA) uncertainty-average; sd of about ± 1.7º
