Philadelphia Area Weather Forecasts

THIS WEEK’S WEATHER

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Friday -Saturday -Sunday

Posted Friday 06/26/26 @ 10:07 AM — The stalled front near us is moving back north as a warm front Friday morning. Very little activity is with this front. Expect showers to end in the area by noon but considerable mid-level cloudiness will remain through the day. It’s possible to see some dim sunshine through clouds early afternoon.

A disturbance moving in from the west will spark some showers and thunderstorms to our south this evening, mostly in Maryland/Delaware and South Jersey.

An interesting trend noted for Saturday. The AI models and the ECMWF maintain a forecast for rain in most of the Delaware Valley on Saturday, BUT many models (GFS, RRFS, RDPS) keep the rain mostly from the city and southward— Areas north and west of the city will have minimal or no rain, according to these models. Here’s a snapshot from the RRFS—


06z RRFS snapshot at noon keeps the rain/thunderstorms mostly from the city on southward on Saturday (Click on image for a larger view.)

This will be an interesting ‘experiment’ where the ECMWF shows considerable rain while the GFS has a different, southern track forecast. (spoiler: over the winter, the GFS did better than the ECMWF in these ‘contests’.) On the side of the ECMWF are the AI models (AIGFS and ECMWF-AI). So some northwestern areas may have better weather than currently forecast.

Stay tuned for my regular “Weekend Weather Forecast” later today.

Thurs Fri Sat Outlook Update

Posted Thursday 06/25/26 @ 2:44 PM — The weakening, cold front will drop through after midnight. Today’s models suggest a bit more shower activity will move in after midnight Thursday into very early Friday morning.

12z RRFS 1 hour precipitation at 6 AM Friday. (Click on image for a larger view.)

It should be noted that the REFS has considerably less rainfall for our area. Both models are new and I’m not able to evaluate this discrepancy.

Both models have the rain ending mid morning with cloud cover thinning Friday afternoon before the next system and warm front move in Friday evening as the warm front moves north and low pressure moves over us.

Saturday looks fairly cloudy and rainy. Sunday looks sunny warm and humid.

AIGFS forecast for Saturday at 2 PM. Hot humid air south of the 760 thickness line (500-1000mb thickness) (Click on image for a larger view.)
Thursday Friday Saturday Forecast Overview

Posted Wednesday 06/24/26 @ 7:46 PM — A weakening low pressure system in southern Canada will attempt to drag a weak front through late Thursday evening into Friday.

18z GFS surface forecast for 7 PM Thursday. Weak approaching front will dissipate as it moves towards us. (Click on image for a larger view.)

Most of Thursday will be sunny or sunny through high cirrus clouds. It will become cloudy after 6 PM as the front approaches. The showers will mostly be to our north and northwest around midnight. Very little rain expected in the city.

Friday will see some scattered showers in the morning but things will quiet down in the afternoon with some sun possible (?)

There’s some uncertainty about the location of the dissipating front for Saturday.

Some models(GFS, Canadian, AI versions) have it right over Philadelphia with some significant rain. The latest RRFS shows it south of the area, moving back as a warm front Saturday evening with thunderstorms. Too soon to be sure, but the AI models have rain for much of Saturday. Things clear by Sunday with more humidity.

Wednesday through Saturday Overview

Posted Tuesday 06/23/26 @ 9:56 PM — Here’s the latest MRMS rainfall totals for Monday night through Tuesday—

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.)

High pressure will build in for Wednesday and Thursday. A system approaches late Thursday into Friday possibly with some light rain, especially areas far north of the city.

Another system approaches late Friday into Saturday.

18z ECMWF-AI forecast for Friday at 8 AM. Friday’s system may stay to our north. There’s a question about how long the Saturday system will linger in our area. (Click on image for a larger view.)

Saturday may be a rainy day, according to the AI models with some predicting 1″ of rain. The regular models have this system moving out Saturday afternoon. Too early to be sure.

Tuesday Forecast Update

Posted Tuesday 06/23/26 @ 10:10 AM — More rain is expected today after much of the region (but not all) received a much-needed significant rainfall. Here’s the MRMS summary estimate of actual rainfall received over the prior 24 hours (9 AM)—

MRMS rain-gauge measured rainfall combined with rain-gauge calibrated and interpolated radar-based summary of ACTUAL RAINFALL RECEIVED from 9AM Monday to 9 AM Tuesday. . Color shading is in inches. Line contour numbers are in mm. (25.4 mm= 1 inch)      (Click on image for a larger view.)

Most models have light rain continuing until later Tuesday afternoon, tapering off from west to east about 3 PM- 5PM.

The southern Jersey shore may have some heavier rainfall later this afternoon. The models have a considerable range in additional rainfall with the AI GFS and ECMWF AI models in the 0.5“– 0.6″ range for the immediate PHL area. with the RRFS and HRRR showing considerably less. Based on current radar, I’m leaning towards the AI model forecasts.

Water Vapor image at 10:17 with superimposed RAP model Vertical velocity (yellow contours_with MRMS Radar and NexRAD radar Note the area of strong upward vertical motion at the Jersey shore, (Click on image for a larger view.)
Tuesday – Another Rainy Day

Posted Monday 06/22/26 @ 7:44 PM — The second half of this system, as described earlier, will arrive Tuesday morning according to the HRRR and a bit later according to the RRFS. There had been a question of when this system would exit and Sunday’s ECMWF-AI model correctly identified it to last into Tuesday afternoon.

While the main placement of the rain has been north and south of our area, parts of the Delaware Valley have already received considerably more rainfall than had been forecast for the entire storm.—

6 PM 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.)

Additional considerable rainfall is expected with the next part of this system, a second low developing near the Virginia Coast—

18z AIGFS forecast for Tuesday at 2 PM showing 6 hour previous rainfall. Considerable additional rain expected tomorrow. (Click on image for a larger view.)

The latest RRFS shows heavy rain and storms again about 3 PM Tuesday afternoon. Rain will be ending much later in the afternoon—

18z RRFS simulated radar forecast for 3 PM Tuesday. Blue=low clouds, maroon=mid-level clouds, tan = high cirrus clouds
Where’s the Rain?

Posted Monday 06/22/26 @ 4:54 PM — That one thunderstorm cell (see previous radar below) blossomed into a swath of heavy rain that went through Center City, according to the 4 PM MRMS—

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)   12 hours Through 4 PM today. The center city accumulation occurred between 2-4 PM   (Click on image for a larger view.)

The rest of our area received the big goose-egg 0″.

More storms are developing to our southwest and northwest and will move through in the next hour or so.

4:52 PM Radar and MRMS radar composite with 700 mb wind streams (green) and vertical motion (omega- yellow contours) (Click on image for a larger view.)

So the forecast for thunderstorms between 2 and 4 PM held for the city, but it’s looking like my Q-vector analysis forecast based on the RRFS model promising a rain-free early start to the soccer game may not hold very long.

Monday Update

Posted Monday 06/22/26 @ 1:45 PM — The latest REFS has the heaviest rain accumulation to the north and the south of Philadelphia by Tuesday evening. This scenario was supported by several models yesterday.

12z REFS shows the heaviest rain accumulation north and south of our area by 9 PM Tuesday. Much of the heavy rain occurs on Tuesday late morning to mid afternoon. (Click on image for a larger view.)

Posted Monday 06/22/26 @ 1:38 PM — Storms are developing to our west, on our doorstep, and the dynamics favor rapid intensification of some of these storms.

New strong cell developed in place ( 1:35 PM) as this area moves into favorable upward motion

Here’s the latest RAP model “SWEAT” index (Severe Weather Event and Threats) with values exceeding 400 in some areas—

RAP model boxed areas show SWEAT index into the severe range (>400) over NJ by 4 PM. (Click on image for a larger view.)

The latest RRFS has backed off on the some of the accumulating rain for today and still shows a significant rainfall for Tuesday mid-day.

Monday Storms Update

Posted Monday 06/22/26 @ 9:06 AM — The system approaching our area is complex and several models show it moving in as two separate but related systems, one later today and another early Tuesday morning. The models still have the largest rainfall to our north.

Today’s 06z ECMWF-AI model forecast for 8 PM Tuesday. Two low pressure centers with rain lasting into the early afternoon. (Click on image for a larger view.)

The focus today has been on thunderstorms that may affect the soccer match later this afternoon. Based on the latest RRFS model, (06z) it appears the heaviest thunderstorm activity this afternoon will be between 2 PM and 4 PM near the city.

As mentioned in a few recent posts, I’ve been using AI to assist with advanced model calculations “tools” for predicting rain and storms. Today is a perfect time to unveil them.

The latest RRFS shows the greatest amount of forcing and dynamics around 2-4 PM today (Q-vector analysis and dynamic vertical motion) —

RRFS Q-vector analysis at 3 PM shows a moderate level of upward motion upstream from the city (orange coloration) with spotty humidity and strong vertical motion in the areas that are red and black. Strong storms over parts of the city at 2-4 PM (Click on image for a larger view.)

Of interest is the Q-vector analysis at 6 PM, showing inhibition of storms over the city.

RRFS Q-vector analysis at 6 PM. Large area of divergence and downward motion (inhibits storms) near the city after the storms departed, which have moved into northern NJ. (Click on image for a larger view.)

The summary statement- based on the above, it’s possible that the soccer game, at least through 5 PM to 8 PM will not be impeded by rain/storms.

While I probably would have better odds betting on the game today rather than betting on my new approach to forecasting with the RRFS, we’ll see how it all works out.

More storms tonight and especially after midnight into Tuesday morning.

Updates later today. Stay tuned.

Update

Updated Sunday 06/21/26 @ 7:00 PM — Over the past two hours, the latest GFS and RRFS models have become available. They show a strong trend towards the rain lasting well into Tuesday (early afternoon) with total rainfall near or above 1” and 2-3 inches in localized areas.

Originally Posted Sun 5:03 PM — The beautiful weather from this weekend will quickly be replaced with clouds Monday morning and then showers and thundershowers as early as the noon hour. (More widespread activity waits for the evening.)

There’s a considerable range of forecasts with this system and the series of graphics that follow demonstrate this—

A strong system currently in the central US will move eastward and affect our weather early Monday with more humidity.

Water Vapor image with superimposed RAP model parameters and radar at noontime Sunday. The warm front will move north of our area Monday and rain associated with this system. Note the fine violet contours near the main low- areas of jet level potential vorticity which will keep this system powerful. (Click on image for a larger view.)

By noontime Monday, light scattered showers will be breaking out in and around Philadelphia; the heaviest rain remains far north and west—

CMC-GDPS wiith AI spectral nudging forecast for 12 PM Monday. Yellow-green is convective precipitation (thunderstorms) (Click on image for a larger view.)

At this point the CMC-GDPS AI diverges from the GFS and ECMWF models and I’ll use the latter two models from this point forward. The CMC-GDPS has the low moving out to sea; the GFS and ECMWF have secondary areas of low pressure with lingering heavy rain—

ECMWF forecast for 8 PM Monday shows heavy rain and thunderstorms over our area. The GFS is similar to the ECMWF. (Click on image for a larger view.)

By Tuesday morning, the GFS still maintains rain into the early morning hours. The ECMWF and CMC-GDPS has the rain offshore with some gradual clearing.

18z GFS forecast for 9 AM Tuesday morning. Lingering showers. (Click on image for a larger view.)

The slower GFS (more rainfall) looks pretty good because the latest ECMWF-AI model is even slower with the exiting rain, with it lasting into Tuesday afternoon—

12z ECMWF-AI forecast for near 8 PM Tuesday evening. Rain lingers with the ECMWF-AI even longer than with the GFS. (Click on image for a larger view.)

So, this will either be a fast-moving system with unimpressive precipitation or it will be a soaker with lingering rainfall well into Tuesday afternoon.

While heavy rainfall for our area was originally forecast with this system, today’s trends seem to be keeping the highest rainfall totals far north of our area, mostly in NY and north.