#Philadelphia #weather #PAwx #PhillyWx #smoke
Friday-Saturday Smoke Update
Posted Friday 07/17/26 @ 8:53 AM — The dark skies this morning is predominantly due to heavy smoke, not cirrus clouds. When trying to see the sun through the smoke, the measurement that captures the dimming is the amount of particulates in the full vertical column of air.
Here’s the current full column “vertically integrated smoke particulates”—
With air quality measurement, the main interest is the smoke that you break, or as they call it, “near-ground” smoke which is really measured/calculated at a height of 8 meters—
No rain today and the near ground smoke level remains high near the city even at 3PM—
Thunderstorms are likely in Philadelphia by 8-10 AM Saturday. By 1PM Saturday. smoke is clearing out near-ground as the winds turn to the southwest—
As mentioned, Saturday looks to be an active day weather-wise. Most models have the heaviest rain to our north, in contrast to forecasts of previous days where the bull’s-eye was right over us.
Several rounds of rain and heavy thunderstorms, one in the morning, several in the afternoon on Saturday. There may be a hiatus between 6 PM and 8 PM, with more storms returning after 9 PM to midnight as a cold front moves through. Details will likely change. Stay tuned.
Friday -Sunday Outlook
Posted Thursday 07/16/26 @ 5:25 PM — The showers predicted this morning by the NAM-NEST did materialize, although they were less extensive than had been forecast. Most of the area saw no activity.
Skies finally clear of most cloudiness on Friday, but the smoke will hang tight. Here’s this afternoon’s 18z HRRR-smoke forecast for Friday afternoon. There will be some short-lived relief in northern sections—
Unfortunately, the model shows this northern clearing to retreat back north by Friday evening into Saturday!
As for Saturday, several energy triggers will converge over us with heavy rain.
The latest ECMWF shows 4 inches of rain over Philadelphia; it’s too early to take this literally.
The GFS also shows many rounds of rain and storms on Saturday into Saturday night, although not 4 inches.
Clearing on Sunday. Sunday looks to be sunny.
Saturday’s weather active weather will require monitoring.
Thursday Update
Posted Thursday 07/16/26 @ 9:57 AM — The current smoke conditions are as bad as had been expected. They should moderate a bit during the day, but still in the hazardous zone. (Total smoke now is estimated to be 120-184 x 10-9 kg/m3. It’s forecast to go to 300 about 10 PM tonight. Normal is 0 – 20 )
Today’s highs—
Several models have light, isolated / scattered showers moving through about 4 PM or so. Of interest is the latest NAM-NEST which shows a large cluster of strong storms moving through Montco/Bucks and part of Philadelphia between 4-6 PM. This model is currently an outlier, but its forecast should be kept in mind.
The extended range forecast- a stormy Saturday with several rounds of showers and storms from early morning (7AM) through midnight. The storms look to become more intense during the evening. Things clear out on Sunday.
Thursday through Saturday Outlook
Posted Wednesday 07/15/26 @ 7:42 PM — Today’s high was 98º at the airport. The expected 100º high temperature was moderated by an increase in haze and smoke, reducing sunshine. It felt very hot despite this due to dew points near 74º.
A wind shift line is moving through Philadelphia right now; winds will shift from the southwest to the north-northwest. Somewhat less hot air arrives for Thursday. Unfortunately, it will bring down some very smokey air into our area.
Once the winds pickup during the morning, the extreme smoke will mix and we’ll be left with very dim sunshine further dimmed by high cloud cover. The smoke may remain with us at least through Friday.
A very stormy Saturday is shaping up, especially towards evening. Most models show showers and thunderstorms moving over the heat ridge and into our area as early as Saturday morning. Several rounds of showers and storms are expected through the day and into the late evening. Heavy rain and some severe storms are possible.
Details over the next day or so.
Wednesday Update
Posted Wednesday 07/15/26 @ 9:41 AM — The smoke/haze will reduce the expected high temperatures today, especially north and west of the city. The airport (who lives at the airport?) may still just reach 100º but I wouldn’t be surprised if it falls a degree short.
Here are the other changes for today:
- Dew points are forecast to be higher, in the low 70s. Despite the slight decrease in temperatures due to the haze/smoke, it will feel more uncomfortable and heat indices may be even higher. The combination of heat and smoke makes this a dangerous situation.
- There’s an increasing chance of a line of scattered showers and thunderstorms moving down from the north between 7 and 9 PM. They may not make it into Philadelphia.
- Smoke. Increased smoke and haze is forecast during the day. The edge of the very heavy smoke reaches the city around 9-10 PM tonight—
By Thursday morning, our area is sitting in serious smoke—
Big Forecast Changes
Posted Tuesday 07/14/26 @ 9:17 PM — There has been a significant change in the forecast which includes the effects of wildfire smoke from Canada. First, wildfires in Canada along with a weak cold front dropping from the north may reduce temperatures on Wednesday and Thursday from previous forecasts.
The smoke plume is impressive and will dim the sunshine, along with making it somewhat hazardous to breath outside. The effects will be most noticeable late Wednesday into at least Thursday.
The GFS captures the wind-shift line (drawn as a cold front) that drops south Wednesday evening—
Some models are showing the possibility of showers and thundershowers Wednesday evening, mostly Bucks county and northward.
By tomorrow morning, I would not be surprised to see further forecast changes. Stay tuned…
BTW, the weekend looks stormy at this time, although the forecast horizon is currently beyond the range of the high resolution models.
All Star Game – Philadelphia
Posted Tuesday 07/14/26 @ 5:13 PM — Temperatures for the All Star Game at Citizen’s Bank Park this evening:
At 11 PM, the temperature will have dropped to 81º with Heat index of 83º.
For Wednesday, the Model Blend high temperatures have come down a bit—
Tuesday-Wednesday Update
Posted Tuesday 07/14/26 @ 10:02 AM — As forecast, the edge of the heat dome is just entering our area this morning. The “576 thickness” is an excellent proxy for the edge of the heat dome—
You can think of the thickness as the lines you would see if slicing through an onion sagitally, in this case, the lines represent lines of slicing through the atmosphere horizontally. This “thickness” is the difference in height of a pressure 1000 mb (near ground) and a pressure of 500mb (about 18,000 feet or a half atmosphere). Higher thickness means that “more atmosphere of lower density (hot) is needed to have it be be 5760 meters in thickness. (or the 576 line). Indirectly, it translates into a proxy for average temperature in this lower half of the atmosphere. ( physics – “Ideal Gas Law”).
Once the heat arrives, we’ll see temperatures reach the 90sº today and near and over 100º on Wednesday
Monday Update
Posted Monday 07/13/26 @ 9:02 AM — The edge of the heat dome, as captured by the 576 thickness contour, continues to push eastward from the upper Midwest.
The models continue to predict temperatures over 100º on Wednesday. Here’s the ECMWF and the Model Blend—
During our last extreme heat wave, the ECMWF’s forecast highs were too high. The Model Blend was very close to actual highs.
These forecast numbers will likely change in the coming days.
Originally Posted Sun 8:38 PM —We had more clouds than forecast Sunday and a few small isolated, short-lived storms developed this evening. The boundary of clouds and rain that moved through Saturday was just to our south, enough to have clouds and disturbances move through. Going back through past models, this morning’s GFS showed this cloudiness and the new RRFS didn’t show it until the 2 PM run.
Hopefully, the forecast for this week will be more straightforward. Basically we have the heat dome punching through from the west (not from the south or southwest). Over the past day or so, all-time record high temperatures have been recorded in the Upper Plains.
The return of the heat dome will move in from the west will bring high humidity and severe heat; several models (Canadian RDPS, ECMWF, German ICON) are forecasting actual temperatures slightly above 100º in Philadelphia for Wednesday. Specifics regarding the heat and humidity will clarify with Monday’s model runs.
I have to laugh… I made a point to remember the date (July 7th evening news 11 PM, ) when one of the weather entertainers who seems to believe she’s more than a “broadcast meteorologist” (in contrast to a real meteorologist who has actual degrees in meteorology and related earth sciences) made the outlandish statement that she didn’t think we would be seeing 100º temperatures again this summer! I said to my wife at that time, “how can anyone, no less a weather person, make that kind of statement the first week in July??”
FYI….There are real meteorologists on TV, including in the Philadelphia area. Back in the 1990’s the American Meteorological Society (AMS) created a category called “Broadcast Meteorologist” which required taking courses and an exam to obtain a certificate. There are probably continuing education requirements as well. The AMS had the excellent intention of trying to assure that the weather person on TV at least knew what a cold front really is. Somehow, the designation “Broadcast” got dropped (just like grade inflation) and now everyone on TV calls themself a “meteorologist”.
It’s unfortunate because it doesn’t allow true meteorologists who know what a Lagrangian motion equation is to distinguish themselves from people who should probably still be called the Weather Girl or Weather Man. (or in my case, theweatherguy, but at least my undergraduate degree was a BS in physics.)
But I digress… Updates this week. Check back.
