Daily Archives: Monday, September 15, 2025 9:39 am

Philadelphia Weather Outlook

THIS WEEK’S WEATHER

#Philadelphia #weather #PAwx #PhillyWx

Thursday Forecast & Looking Ahead

Posted Thursday 09/18/25 @ 8:42 AM — Many areas had much-needed rain on Wednesday. The general forecast for the rain to miss northwest areas seemed to hold, but as is usually the case, the exact model forecast for the heaviest rains was not all that accurate.

MRMS rain-gauge measured rainfall combined with rain-gauge calibrated and interpolated radar-based summary of ACTUAL RAINFALL RECEIVED. Color shading is in inches. Line contour numbers are in mm. (25.4 mm= 1 inch)      (Click on image for a larger view.)

For today through Saturday, expect sunny skies and mild temperatures. Friday is forecast to have highs in the mid to upper 80s, but during the late afternoon into Saturday morning, it will become quite windy.

Again, despite TV forecasts for a great weather weekend, the models have been forecasting considerable cloudiness for Sunday. This is due to a strong, jet stream level short wave moving through as moisture aloft moves in from the southwest. For the Eagles game, the winds will be light from the east.

06z GFS forecast for Sunday at 4 PM. Jet stream level 250mb height “short wave” moves through bringing cloudiness Sunday. (Click on image for a larger view.)
Wednesday Forecast Update

Posted Wednesday 09/17/25 @ 8:54 AM — We are at the northern fringe of the precipitation shield of the coastal storm. The storm is expected to weaken during the day, but not before some showers move in to the Philadelphia area, especially southern sections, Chester and Delaware Counties.

This morning’s radar shows showers rotating in from the east around the coastal system near Virginia. (Click on image for a larger view.)

The latest REFS continues to show showers on and off during the day and afternoon hours; heavier showers southern sections.

06z REFS forecast for 1 PM. Rain shouldn’t move much further north than shown. (Click on image for a larger view.)

Clouds and showers dissipate Thursday morning with sunshine breaking out in our region. (Showers linger at the Jersey Shore.)

Tuesday Forecast Update

Posted Tuesday 09/16/25 @ 9:23 AM — Yesterday’s water vapor image suggested that the coastal system was moving faster than previously forecast. We had some cloudiness on Monday and we have considerable cloudiness today.

Radar at 8:40 AM Tuesday (Click on image for a larger view.)

Despite current radar, the RRFS and REFS guidance suggests that many areas north and west of Center City will remain dry for much Tuesday. It will be a different story southeast, in southern NJ and the shore, where rain is already moving in.

10z RRFS forecasts rain from Center City and south. Northwestern suburbs will likely miss the rain for much of the day Tuesday. (Click on image for a larger view.)

The current REFS is forecasting light rain through Wednesday. Rainfall amounts are still expected to be light from the city northwestward.

00z REFS total rainfall forecast through Wednesday. These amounts are similar to the ECMWF and NBM (Click on image for a larger view.)

Rain moves in from the city and northward during Tuesday evening and night time hours.

Originally Posted Mon 9:39 AM —A coastal system associated with a closed upper level low will be the weather maker this week. This system was correctly forecast by the ECMWF-AI model as early as the end of last week.

The current WV image suggests a faster system, arriving Tuesday afternoon in our region—

Current satellite water vapor image with superimposed RAP model 500-1000 mb thickness lines (yellow), Mean Sea Level Pressure isobars (black contours) potential vorticity (fine violet contours) with superimposed MRMS RADAR. (Water Vapor Imagery reveals emitted water vapor infrared energy associated with temperature and height, NOT reflected light from clouds.) (Click on image for a larger view.)

Here’s the latest ECMWF-AI forecast for Tuesday afernoon—

06z ECMWF-AI forecast for Tuesday afternoon. (Click on image for a larger view.)

Blocking high pressure to our north will unfortunately limit the amount of much-needed rainfall that reaches the immediate Philadelphia area.

Currently, only 0.3 inches of rainfall is forecast, less north and west of the city from late Tuesday into Wednesday.

Skies clear during the day Thursday.