Daily Archives: Sunday, October 26, 2025 7:24 pm

Philadelphia Weather Outlook

THIS WEEK’S WEATHER

#Philadelphia #weather #PAwx #PhillyWx

Thursday’s Total Rainfall

Posted Thursday 10/30/25 @ 4:11 PM — We had much-needed large scale rainfall for about 18 hours.

Here’s the MRMS based rainfall totals:

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)   This is a “pass 2” calibration.   (Click on image for a larger view.)

There may be a few additional scattered showers over the next few hours.


If one looks at the model forecasts below, the band of heavy rainfall just west of the city was picked up by the REFS and RRFS, but the totals were too high, a known issue with these models.

All models missed the additional heavy banding of rain in NJ as well as the faster speed of the system. According to the RTMA, wind gusts near 50 mph were common in NJ around noon.

Things will be quiet through early Monday.

Thursday Rain Update

Posted Thursday 10/30/25 @ 1:56 PM — The signal for a faster storm has been there since last night and the latest RRFS hourly shows some sun breaking out from west to east between 3 and 4 PM. The same RRFS shows a few widely scattered showers, highly localized, that move through until about 7 PM.

Visible Satellite at 2:35 PM with superimposed MRMS radar. Breakup of clouds to our southwest may give us some peeks of sun. (Click on image for a larger view.)

Posted Thursday 10/30/25 @ 10:09 AM —

Current conditions about 10 AM (Click on image for a larger view.)

Posted Thursday 10/30/25 @ 9:38 AM — The model trends from last night continue to hold true. The area, based on the latest MRMS, has received 0.75″ to 1″ of rain with more on the way.
The latest RTMA suggests that the storm is continuing to move somewhat faster than forecast. Rain will likely taper and end from southwest to northeast between 7 PM and 9 PM.

The heaviest rain and highest winds will be around noontime near Philadelphia and into NJ into the afternoon hours. There’s a chance of thunder. Wind gusts approaching 50 mph are possible.

RRFS Meteogram (winds and gusts) for Blue Bell—

Meteogram winds and gusts Blue Bell PA Arrow is noon. (Click on image for a larger view.)
Thursday Rain Update

Posted Wednesday 10/29/25 @ 10:05 PM — None of the models (including tonight’s HRRR) show the area of rain that is about to enter the immediate Philadelphia area. That casts some doubt on the accuracy of the model forecasts. That said, the afternoon HREF, REFS and RRFS as well as the Canadian HRDPS still support high rainfall levels in the immediate PHL area.

Here’s the latest REFS—

18z REFS PMM (probability matched mean) rainfall forecast for Thursday’s storm. (Click on image for a larger view.)

Rain may end earlier, as early as 9 PM Thursday near the city.

Posted Wednesday 10/29/25 @ 9:23 PM — Additional models show the following trends—

  • This afternoon’s 18z models suggest a faster moving system and an earlier exit of the rain.
  • Current RTMA data shows greater pressure changes than model forecasts.
  • Current radar shows a band of heavier rain already in northern Delaware.

I’m still leaning towards the high rainfall amounts of the RRFS (below).

Posted Wednesday 10/29/25 @ 5:03 PM — As is very often the case, the predicted rainfall has shifted with additional model runs and there’s wide ranges in forecast rainfall as well as differences in where the rain bands will set up. The timing elements remain the same: the rain starts near the city as early as 11 PM tonight and is widespread by 2AM Friday morning.

As for the forecast total rainfall, let’s start with the latest NBM and its updated precipitation with the 19z model run—

Let’s move to the RRFS (experimental but soon to become operational in early 2026)—

12z RRFS forecast total rainfall by 12 AM Friday morning. (Click on image for a larger view.)

The ensemble version of the RRFS, the REFS, combines twelve time-lagged runs of the model statistically—

The Canadian High Resolution HRDPS—

12z HRDPS forecast total rainfall by 12 AM Friday morning. (Click on image for a larger view.)

Finally, the HRRR—

18z HRRR forecast total rainfall by 12 AM Friday morning. (Click on image for a larger view.)

As is the case with snowstorms, the bet on which model is best capturing this storm is anyone’s guess. I’m putting my money on the REFS, but I know it has a tendency to over-forecast rainfall. I’ll do some other assessments later and I’ll post again.

Wednesday Forecast & Heavy Rain Thursday

Posted Wednesday 10/29/25 @ 8:58 AM — Today, Wednesday, will be mostly cloudy, although several models show some sunshine for a few hours early to mid afternoon mostly northwest sections of our area. Otherwise, windy and cloudy.

Rain from the large complex storm moves in to our area around midnight and will be quite heavy in some locations, especially during the afternoon hours on Thursday. Some thundershower activity possible. It will also be quite windy.

The most recent pre-release models of the RRFS and REFS are showing heavy rain in our area for Thursday. (We need the rain!) I’m increasingly using these pre-release versions of these new models for my forecasts.

00z REFS model total rainfall through Thursday. (As always, the exact amounts and locations of the heaviest rain are often not accurate, but it gives and idea of the expected rainfall in the area.) (Click on image for a larger view.)
Tuesday’s Forecast & Thursday’s Storm

Posted Tuesday 10/28/25 @ 9:37 AM — The latest model guidance confirms the trends noted in yesterday’s storm update.

First, Tuesday— the thin cirrus cloud cover we see now will be replaced by somewhat thicker mid-level cloudiness around noontime, especially from near the city and southeast. Blocking high pressure to our north may build and clear skies again around sunset, especially western areas.

Wednesday — Periods of clouds with interspersed periods of bright skies and sun. The showers forecast for the Jersey Shore aren’t showing on the current RRFS model, but the ECMWF does show some light precipitation at the some of the NJ Shore on Wednesday.

Thursday— The trend now is for the rain to wait until the pre-dawn hours with heavy rain and gusty winds.

06z GFS model forecast for 2 PM on Thursday. Afternoon will be peak heavy rainfall. (Click on image for a larger view.)

Total rainfall now about 1.5-3 inches for much of the area.


Friday— Rain ends before daybreak. Some models show instability cloudiness; some show more sunshine. All show windy conditions with temperatures around 50º for Trick o’ Treaters Friday early evening.

Thursday’s Storm

Posted Monday 10/27/25 @ 10:58 AM — The forecast for the large low pressure system to affect our area late Wednesday into Thursday continues to evolve. Here are the current model guidance trends—

  • Secondary low pressure formation is again forecast to occur off of the southeastern coast, perhaps with multiple centers. The weekend models had this occurring much later and closer to the Mid-Atlantic.
  • The system will approach earlier and exit earlier. The rain associated with this storm will be gone by Friday (Halloween), although winds associated with the system will likely be affecting our area.
  • Rain may start as early as Wednesday afternoon at the NJ Shore and most areas just south of Philadelphia by the evening.
  • Rainfall is forecast to be in the 1.7″-3″ range with locally higher amounts possible.
  • Wind gusts exceeding 40 mph will be with us on both Thursday into Friday.
Today’s 06z GFS forecast for Wednesday evening at 7 PM. Rain already affecting the NJ Shore (Click on image for a larger view.)

Total rainfall through Friday morning—

Today’s 13z NBM total rainfall forecast through Friday morning. (Click on image for a larger view.)

Why is the immediate Philadelphia area missing out on the heaviest rainfall over the past year??

Originally Posted Sun 7:24 PM —The models have finally come together with a reasonable forecast for this week and for Halloween, and I’ll be using the NAEFS to take us through the week.

The system originally expected to give us rain on Tuesday will stay to our south; the system expected to spawn a coastal low in the southeastern US will not occur as previously forecast, but instead will spawn low pressure over the Mid Atlantic region on Thursday.

Right now, low pressure in the central US will move to our south as a pool of cold air and blocking high pressure keeps it suppressed to a southern track—

NAEFS model statistical “mode” version with overlayed GEFS model “bias-corrected” precipitation for Sunday night Blocking high pressure keeps the track to our south. (Click on image for a larger view.)

By Wednesday, a new bolus of energy develops another upper low in the Central US as high pressure block weakens over us—

NAEFS model statistical “mode” version with overlayed GEFS model “bias-corrected” precipitation forecast for Wednesday morning. This is a NEW system i the central US (Click on image for a larger view.)

By Thursday, a secondary low develops over the Mid Atlantic coastal region and we’ll finally get some large scale much-needed rain. Melissa, in the western Atlantic, will be moving out to sea.

Combined 18z NAEFS (mode version) forecast with Bias-Corrected GEFS model 6 hour precip for Thursday evening (Click on image for a larger view.)

Thursday looks to be quite stormy with heavy rainfall exceeding 1 inch or so. We are in such a rain deficit, it will be good if this happens.

The storm is expected to exit just before the Trick or Treaters come around late Friday. It should be a mostly rain free Halloween evening.

There are signs that the rain may end even earlier on Friday.