Monthly Archives: October 2025

Philadelphia Weather Outlook

THIS WEEK’S WEATHER

#Philadelphia #weather #PAwx #PhillyWx

Friday and the Weekend Outlook

Posted Thursday 10/23/25 @ 6:00 PM — This morning’s high resolution models (12z HRRR, RRFS and NAM-NEST ) all got the cloud cover wrong, but some global models which came out after my update (12z GFS, ICON ) continued to show the cloud cover that did actually develop. Go figure.

There isn’t much happening weather-wise this weekend. The notable exception is the colder temperatures at night. Tonight, many areas just outside the city will see the upper 30s.

18z NBM forecast low temperatures by Friday morning. All temps above are around ± 1.2º (Click on image for a larger view.)

I’m keeping my eye on next week’s potentially stormy weather. Some models continue with the development of a very wet secondary coastal low system; other models show blocking high pressure keeping the rain away from our immediate area. Stay tuned.

Thursday Forecast

Posted Thursday 10/23/25 @ 12:29 PM — Several models seem to have removed the cloudiness forecast for this afternoon that they were all showing yesterday.

Posted Wednesday 10/22/25 @ 5:25 PM — I didn’t focus on any forecast specifics for today (Wednesday), but we had an area of moisture aloft with cold air instability this afternoon resulting in the low level stratocumulus cloudiness that moved in. This will dissipate tonight.

Another area of moisture will rotate into our area from the northwest on Thursday with similar cloudiness developing between 12 and 2 PM, then dissipating around sunset.

Next week is again looking interesting, weather-wise, with a closed upper low inducing coastal low pressure development. There are large differences in timing and specifics, but we may finally get some decent rainfall next week according to the ECMWF-AI and the NAEFS. It looks like any storminess will end in time for Halloween.

Latest ECMWF-AI forecast for Tuesday 2 PM. (Click on image for a larger view.)

Forecast Review

Posted Wednesday 10/22/25 @ 10:01 AM — The rain last night equaled or exceeded the upper limits of the forecast rainfall amounts and the rainfall coverage exceeded most models’ forecasts. The intensification I spoke of did occur, but it was mostly offset by the speed of the precipitation shield. Here’s the MRMS totals for this rainfall—

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.)

Posted Wednesday 10/22/25 @ 10:01 AM — Increasingly seasonably colder weather for the next several days. No rain expected until some time on Monday, The tropical system in the Caribbean increasingly looks like it will move away from the US. The storminess I spoke of for next week is now uncertain.

Wednesday Night- Interesting Weather

Posted Tuesday 10/21/25 @ 7:37 PM — The forecast for cold front expected to move through tonight has been nothing special with only scattered showers and rainfall amounts on the light side (0.0- 0.13″)

I’ve been looking at the current hourly models and I’m seeing things that don’t translate into this simple low rain forecast—

  • Radar echos are indicating somewhat more rainfall occurring to our west than model guidance.
  • Vertical velocity Pressure (Omega) is very significant just to our southwest indicating potential secondary low formation.
  • Three hour pressure tendencies are suggesting secondary low pressure forms near our area.

I’m going to go out on limb and post that there’s the potential for somewhat more rainfall than has been the official forecast. I may be wrong here, but these occasional weather ‘experiments’ are part of my fun of doing these forecasts. As I always say, I guess we’ll see. We could use the rain.

Radar with RAP model vertical velocity pressure (Omega) and 700 mb wind streams. Strong development to our southwest is greater than forecast previously. (Click on image for a larger view.)
22z RAP model forecast Vertical Velocity Pressure at 700 mb. Strong upward motion. Not as much low level moisture as I would expect. (Click on image for a larger view.)

BTW, for weather nerds, the middle and end of next week (just before Halloween) is looking quite interesting and stormy here.

Tuesday

Posted Monday 10/20/25 @ 4:54 PM — Tuesday will be sunny for most of the day and will become mild with highs 69º-70ª. Another strong cold front moves through around midnight into early morning Wednesday. Rainfall with this front will be scattered and on the very light side with accumulations of 0.10″ or less. Windy and gradually colder on Wednesday and colder Thursday.

ECMWF-AI model forecast 2 AM Wednesday. The red and magenta ‘thickness lines’ demarcate very cold average temperatures to this air mass.

Mon 4:17 PM —Forecast Review —Based on the visible satellite loop (and looking out the window), we had much more instability cloudiness this afternoon than forecast. Even today’s 8 AM model runs (12z) of the HRRR and RRFS failed to show the extent of cloud cover this afternoon. Only later model runs of these hourly models captured the widespread cloudiness. The ECMWF-AI model did forecast this cloudiness.
Monday Update

Posted Monday 10/20/25 @ 9:24 AM — The approaching upper trough will cause a period of cloudiness. The showers will miss us. Expect the sun to return from southwest to northeast between 12 PM and 2 PM.

Radar at 9 AM with superimposed RAP model Omega. (Click on image for a larger view.)

BTW, we had between 0.13″ and 0.30″ of rain early this morning. Most areas received at the lower end of this range, at best.

Sunday Evening Update

Posted Sunday 10/19/25 @ 7:45 PM — Current radar is a case-in-point for why I rarely use the word “tracking” regarding weather. Radar shows storms that look to be on a straight “track” to hit Philadelphia.

Current Radar 7:30 PM Sunday with superimposed RAP model low level Omega as dashed yellow contours in red box. (Click on image for a larger view.) (Omega is shown as -ubars/sec not, + ubar/sec where negative values are actually negative of a negative value which is really positive Omega. Confusing, huh? )

But, radar alone doesn’t tell the whole story. A very strong area of Omega (downward vertical motion – yellow dashed contours in red box) is between us and the storms, according the latest hourly RAP model. If the RAP model is correct, this downward motion will reduce the intensity of the line of storms as it moves closer to our area. Hence, the reason for low rainfall totals here.

Monday

Originally Posted Sun 5:20 PM —A sharp cold front moves through after midnight tonight. As has been the case recently, the heavier rain will stay to our far north and west. That said, Philadelphia and its surrounding counties may get anywhere from 0.17″- 0.30″ of much-needed rain. The trend over the past day or so has been towards less rain and the lower range. The story tonight with the front will be gusty winds.

A sharp upper trough moves through about 10AM Monday. Winds and cloudiness (especially from the city northward) will accompany this fast moving trough. Skies clear again in the afternoon. The big story Monday will be the windy conditions with sustained winds just under 15-20mph and gusts over 30 mph.

Another cold front moves through Tuesday night into Wednesday, also with very light showers.

ECMWF-AI forecast for Tuesday at 2 PM Cold front moving through western PA at that time. NOTE the appearance of the RED 540 thickness line. In winter, this indicates temperatures in the mid/upper atmosphere are cold enough to support snow. This is really the first significant dip of cold air this season for us. (Click on image for a larger view.)

Thursday will be quite cold compared to recent weeks.

Philadelphia Area Weather Forecasts

WEEKEND WEATHER FORECAST

#Philadelphia #weather #PAwx #PhillyWx

Sunday Forecast Update

Posted Sunday 10/19/25 @ 8:42 AM — We’ll have sunny skies through high cirrus clouds today. Thickening cloudiness is expected from west to east between 5 PM and 7 PM. The winds and wind gusts will be increasing this afternoon during the Eagles game and gusts in the range of 30-40 mph will become increasingly likely, especially after 10 PM as the cold front moves through.

The model guidance has backed off on the heavy rain for tonight (after midnight); surface low pressure along the front is expected to develop in southern New England, robbing our area of the energy (and the heavier rain). As always, there’s a range of rainfall amounts from model to model, but the overall range is from 0.20″ to perhaps 0.45″. Locally heavier amounts possible, occurring between midnight and 3 AM.

07z NBM accumulated rainfall forecast by Monday morning. As always, the model depiction of the rainfall amounts is rarely to be taken literally. Just a guide. (Click on image for a larger view.)

While clearing is expected early morning, the negatively tilted upper air low may cause some instability cloudiness to develop Monday, late morning into the afternoon, especially from the city northward.

Saturday Update


Posted Saturday 10/18/25 @ 10:01 AM —

10z RRFS forecast for noon Saturday (Click on image for a larger view.)

A fasting moving sharp line of showers and storms is still forecast for the hours after midnight Sunday into Monday morning.

Originally Posted Fri 6:06 PM —An upper level ridge and high pressure will bring mostly sunny skies and milder temperatures through the weekend. A brief exception will be a bit of cloudiness mid-day Saturday. Things change abruptly after midnight Sunday into Monday with a line of heavy showers.

A cold front moves through Sunday late evening/night. The models have been consistent with this forecast and a slight change has been for the main area of precipitation to move through a bit later, about 9-11 PM. It’s also appearing that a line of heavy showers/thunderstorms may move through 1AM Monday morning with high winds.

ECMWF forecast (temperature-shading) pressure and surface winds (Click on image for a larger view.)

Saturday

Sunny early. Some mid-level cloudiness especially western and northwestern sections late morning into early afternoon as a mid-level disturbance moves through over the upper level ridge. Clouds dissipate later in the afternoon.

High Temperatures— Blue Bell: 69º Philadelphia 70º
Very low uncertainty based on standard deviation ± 0.6º

Sunday

Sunshine through high cirrus clouds and mild in the afternoon. Quite breezy/windy early afternoon becoming very windy by evening.

High Temperatures Blue Bell: 76º Philadelphia 77º
Very low uncertainty based on standard deviation ± 0.6º

Sunday night into Monday

Strong wind gusts…briefly strong rain squall with embedded thunderstorms moves through between midnight and 3 AM Monday morning. Rainfall amounts have risen to about 0.4-0.6 inches with locally higher amounts.

Philadelphia Area Weather Forecasts

THIS WEEK’S WEATHER

#Philadelphia #weather #PAwx #PhillyWx

Quiet Weather through Most of Sunday

Posted Thursday 10/16/25 @ 7:47 PM — Not much happening weather-wise over the next three days. Cold front in upper midwest will slowly advance towards us. Warmer flow of air ahead of the front will bring
temperatures into the low 70s by Sunday.
Showers associated with this front will likely waituntil Sunday evening (6-10 PM) before moving into the immediate Philadelphia area.

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 temperature, NOT reflected light from clouds as is the case with visible satellite imagery. (Click on image for a larger view.)

Rainfall with the front late Sunday evening through around daybreak Monday will be light. The NBM shows rainfall totals of 0.3″-0.5″

18z NBM total rainfall by Monday Black Contours are 0.1″ spacing. (Click on image for a larger view.)
Wednesday-Sunday

Posted Wednesday 10/15/25 @ 8:31 AM — High pressure at the surface and an upper level ridge builds in for the next several days, giving us beautiful Fall weather. On a more granular level, an upper level jet streak moves through later this morning (Wednesday); some models have a brief period of cloudiness here, some don’t. A difficult call.
Temperatures are expected to be in the upper 60s and maybe low 70s.

Earlier this week, it appeared that some near-80º temperatures would be with us Sunday. That’s no longer the call, but still mild in the low 70s. A strong cold front moves through Sunday night into Monday morning with some rain. The Eagles game will see nice weather, but it may be windy ahead of the cold front.

ECMWF-AI forecast for Sunday at 8 PM

Tuesday -Wednesday

Posted Monday 10/13/25 @ 5:33 PM — Plenty of clouds on Tuesday with some brightening possible mid to late afternoon. We’ll finally see the sun on Wednesday. It will be windy both days. Tuesday high 67º Wednesday high 67º-69º

Forecast Review

Mon 4:50 PM —Forecast Review — The storm isn’t over yet, but a number of things stand out— the forecast wind gusts and rainfall accumulation were much lower in magnitude than originally forecast in and around Philadelphia.

What looked to be a drought buster was simply a bust as far as meaningful rainfall. Of course, a different story at the NJ Shore which was was more accurately forecast.

While the storm is not over, here’s the multi-day total of actual rainfall—

4 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.)

The current radar around 4:30 PM shows what’s been happening for the past two days: rain drops along the coast and there’s not enough lift and dynamics to continue the rain inland—

Radar image with superimposed RAP model maximum Omega (vertical motion). The rain doesn’t make it much past I-95. (Click on image for a larger view.)

You might ask why? While there’s a surface low and even a mid level low over our area, the upper air (jet level) is anticyclonic in shape and the I-95 corridor lies in an area of descending air from the jet streak to our west. Here’s the RAP model output that demonstrates this—

Jet stream level winds (colorized) with white arrows The red rectangle is an unfavorable location for the upper motion needed for rain. The fine concentric blue contours are favorable areas. (Click on image for a larger view.)

Forecast Update

Posted Sunday 10/12/25 @ 10:05 PM — For Philadelphia and westward, very light rain overnight. Somewhat light to moderate rain moves in from the southeast about 10 AM Monday and tapers off around or after midnight Monday into Tuesday. For the NJ Shore, moderate rain tonight becoming heavy again Monday with high winds.

18z REFS probability matched mean precipitation. (Click on image for a larger view.)

Originally Posted Sun 5:49 PM —This week’s weather picks up where the weekend’s coastal system left off. Heavy rain and high winds have been battering the New Jersey Shore, but as forecast here last night, the amount of rain inland, from the I-95 corridor westward, has been minimal.

The coastal low has elongated and split into two systems, notably forecast by the ECMWF yesterday—

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 temperature, NOT reflected light from clouds as is the case with visible satellite imagery. (Click on image for a larger view.)

The northern system will intensify and bring rain and winds further inland tonight and especially Monday.

Here’s the current conditions using the RTMA. I’ve drawn the track of the two lows based on the ECMWF forecast—

5 PM RTMA wind streams with 3 hour surface pressure tendencies. Track of the lows is based on the ECMWF. (Click on image for a larger view.)

The models continue to over-forecast rainfall for the immediate Philadelphia area and west of the I-95 corridor. The latest model forecasts range from 0.20″ to 0.50″ rainfall by daybreak Tuesday morning. I’m leaning towards the lower range for most locales based on the RRFS which correctly forecast the paucity of rain we had here today.

Winds will continue to increase.

Winds and Gusts Meteogram for Blue Bell PA

This is an interesting storm. Check back for updates.