Philadelphia Area Weather Forecasts

WEEKEND WEATHER FORECAST

A reasonably decent weekend is on tap weather-wise, especially since the threat of the remnants of Hurricane Delta will take take their time moving into the Philadelphia area. A few days ago, the rain was expected to arrive as early as Saturday.   Rain may wait until Sunday evening!

High pressure to our northeast and a strong upper air ridge will weaken Hurricane Delta once it moves inland and delay its advance towards us. However, a flow of moisture in the mid and upper levels  of the atmosphere will cause some high cloudiness to develop on Saturday.

On Saturday, we’ll still be under the influence of high pressure, but a layer of upper level clouds will move in.  The sun often shines through this thin cloud layer.

HIRESW Cloud Ceiling 2PM Saturday  (Click on image for a larger view.)

(The cloud forecast is a bit tricky on Saturday.  The NBM model blend shows high uncertainty in our area regarding the degree of cloudiness, by a factor of almost 40% in either direction!)

Saturday—

  • Sunny in the morning
  • High cloudiness layer in the afternoon, slowly fading sunshine
  • NBM high temp 76.3º  sd 2.5º (high spread/lower confidence)
  • Winds SW 10-15mph with a few higher gusts in the afternoon

On Sunday, high pressure departs to the northeast and an easterly wind flow develops.

 

Sunday—

  • Cloudy, some sun possible in the early morning.
  • Cloudy by afternoon
  • NBM high temp 74.3º sd 3.0º (high spread/lower confidence)
  • Light scattered sprinkles possible after 2 PM
  • Rain after 4-6 PM
  • Winds E 10 mph, increasingly gusty in the afternoon.
GFS 1 hour Precip/wind/cloud cover 5 PM Sunday  (Click on image for a larger view.)

About 1 inch of rain is currently forecast through Monday, according to the NBM.   The GFS has almost 2 inches of rain!

Philadelphia Weather Outlook

STORM DELTA WEEKEND UPDATE

Thursday 8:05 PM Update — The latest models continue to push the start of the rain later in the day on Sunday, now late afternoon.

The weekend is looking much better, as the circulation of Hurricane Delta will fall apart as it moves into an upper air ridge environment on the East coast.

Here’s the [latest  available on public web] Navy COAMPS model forecast for Hurricane Delta—

Navy COAMPS Tropical model  (Click on image for a larger view.)

 

The trend has been for the rain to move in later on Sunday.

Saturday will see high cloudiness move in in advance of the tropical moisture

The models have pretty much lined up with yesterday’s Model Blend, having the precipitation wait until Sunday afternoon for the Philadelphia area.  The NBM (Model Blend)  has light rain starting in the mid afternoon, but several models hold it off until late Sunday afternoon. 

Here’s the latest Model Blend (NBM) precip forecast for 3 PM Sunday—

NBM 1 hour accumulated rain forecast 3 PM Sunday  (Click on image for a larger view.)

Rain slowly increases in intensity during the late afternoon and evening.  Heaviest rain on expected on Monday.

This will be plain rain event, especially late Sunday through Monday.  About 1-1.5 inches of rain is expected by late Monday afternoon.  Nothing like Isais.

Weather… and Other Things 'Up in the Air'