Of meteorology and atmospheric science at Penn State.

This is weather world.

Good evening and welcome to Weather World on this Friday, September 5th, 2025.

I'm your host, Filippo Formica.

Alongside our forecaster Carl Schneider.

And Carl, today was a brief respite from the rain, but we're bringing on a soggy Saturday.

Yeah, soggy for parts of the state.

I think they'll be salvageable times.

And then by the time we get to Sunday things dry out.

So it's looking really like a nice end to the weekend.

Looking forward to that forecast from Carl.

Also on tonight's show is the rest of our Friday forecast frenzy.

With two full weeks of forecast going out to the latter half of September.

But first, here's Carl at the wall.

Thanks very much, Filippo.

Some unsettled weather in store for us this weekend that will lead into a very nice and quiet end to the weekend.

I'll have those details here over the next few minutes.

We'll start out with a look at the four camera view across the Commonwealth.

It's really been a mix of clouds and sun over most areas.

You'll also have noticed a thin, milky overcast through much of the state.

That's thanks to some wildfire smoke that's mainly been in the upper levels.

That's going to be on the way out here over the next few hours, but the regular cloud cover is going to be on the way in and is going to be a theme here of the next 24 hours or so before things change.

By the time we get to Sunday, the radar and satellite picture looks relatively inactive right now, but there's some features we should watch this enhanced area of cloud cover in eastern Ohio that's moving into western Pennsylvania.

That's along a surface cold front.

That's really the dominant feature here in our short range forecast.

And I'm watching these areas in southwestern Pennsylvania for possibly the development of some showers and thundershowers would probably be after dark this evening.

Those are going to be an issue mainly for areas along to the west of I 99 going through the overnight hours.

As this front progresses, east areas in eastern Pennsylvania will have to worry about rain going into the day tomorrow.

The temperature map shows that ahead of this front, temperatures have rebounded nicely low to mid 80s in the southeast, 70s in the high ground.

I think in southeastern Pennsylvania.

We're going to be at similar numbers tomorrow afternoon.

But in the west, as that cold front moves through, temperatures will be tumbling and we'll have a very fall like feel even as early as the afternoon tomorrow.

We can really see where that cold front is here on the dew point map that gradient in the dew points right about at the Lake Erie shoreline ahead of that dew points in the 50s and even 60s.

And I think these values will increase as we go through the overnight hours, reaching around 70 by tomorrow.

So it could be a bit muggy in southeastern PA before that cold front moves through tomorrow night, and it will be a refreshing air mass in its wake as we look off to the west.

So the national satellite and radar picture shows some of our main weather features.

There's the surface low, where this surface cold front is attached to spinning to the north in Canada, we're watching this area along the front in the Ohio Valley for the development of some showers and storms overnight tonight, and whether that occurs is going to determine how much rain comes in here overnight tonight.

I think there's still the risk of some light rain reaching areas in western PA late tonight, even if it doesn't rain earlier in the night.

And then the mid-level disturbance associated with the rain here in Missouri and Kansas will get here tomorrow afternoon.

That's going to provide some more lift for showers and storms to develop in eastern Pennsylvania tomorrow afternoon.

So the temperature map, you can clearly see where the cold front is stretching through the Midwest behind it, a very comfortable fall like air mass.

And that will start to arrive in northwestern PA tomorrow and will be here present for all of us through the day Sunday.

So our evening service map shows that surface cold front moving through this evening.

We'll have to watch for some showers and storms to develop along it.

That scattered activity mainly in Western PA.

I think it's a dry night in eastern Pennsylvania.

Then as we go through the overnight hours, possibly a couple of rounds of rain, but most of the action will be tomorrow.

Definitely not a washout.

Some areas will see more rain than others.

I think the heaviest rain could occur late in the day along the cold front, with some showers and storms in eastern Pennsylvania, but behind that, that's where the clouds clear out and high pressure settles in.

So it's going to be a very nice and comfortable end to our weekend.

By the time we get to Sunday afternoon.

So our forecast for tonight, that's going to show that we're becoming unsettled in western Pennsylvania.

Again, the possibility for some scattered showers and rumbles after dark.

Round of showers entering western Pennsylvania late in the night as well.

Lows anywhere from the upper 50s in the west, hanging on to some mild conditions in the upper 60s to around 70 in the southeast on Saturday.

Number of rounds of rain, but not a washout for all.

Most of the shower activity should be in the morning hours, with the dry afternoon in the west.

Scattered light rain through parts through times of the day in central PA, I should say, with the main shower and storm threat in southeastern Pennsylvania.

By the time we get to the afternoon Sunday.

Really nice day.

I'll have more details on Sunday's forecast coming up in just a few minutes.

It looks like high pressure is once again going to dominate the extended forecast period, which means we are not going to see much in the way of rain if we see any at all.

Before we get to that forecast, here's the water vapor satellite imagery once again gives us a good look at the steering winds in the upper levels of the atmosphere, and it's really hard not to notice this, this big ball here of counterclockwise circulation in east central Canada.

And that's unleashing the cooler air on parts of north central United States.

And as we get to Monday, which is when our extended forecast period begins, we start to see that trough lift out.

There's a big ridge once again across the western US, even into western Canada.

That trough is lifting out.

We still are under the influence of northwesterly flow aloft as that exits.

So I think Monday is going to be a bit on the cooler than average side across the Commonwealth.

But as we go into the middle part of the week, those steering winds change more of a southwesterly flow.

So I think we're going to start warming up as we go into the middle of the week, getting to average and maybe even above average a little bit.

By the time we get to the end of the week, another trough is going to lift through, but it's not going to be bringing much of a punch at all.

I think it will bring cooler air by the time we get to the end of the week, but not much in the way of precipitation.

Why is that?

Because there's just not much moisture available.

We can see that here on the moisture tracker.

We're sticking with the European model.

The brighter colors here indicate where there's more moisture available in a column of air from the ground up to cloud level, where you don't see anything.

That's where there's dry air and no precipitation is expected.

We also have these isobars here, lines of equal pressure with the clockwise circulation.

Here you can see this dominant high pressure system to start our workweek.

And that means dry conditions, not much in the way of wind and dry days in store for Monday as well as Tuesday.

We're also going to start the mornings off on the cooler side, so keep that in mind.

If you live in northwestern Pennsylvania, where you could see some patchy frost.

By the time we get to Wednesday, we start to see that high move off to the east.

Our flow changes a little bit, so we start warming up a little.

There is going to be a there's an indication of a low pressure system forming along the southeastern coast that could move up the Atlantic seaboard, but right now, I think it's going to stay far enough to the east that eastern Pennsylvania won't be impacted by it.

There is a weak front to our northwest that will move in on Thursday, but notice not a lot of moisture available with it.

I think the dry air is really going to win out in this one.

So if any precipitation falls, it's going to be very light and I think it will be mainly in northern Pennsylvania.

The biggest impact of this front is going to be cooler air that slides in for the end of the workweek.

So looking at this extended forecast, it's going to start out cool on both Monday and Tuesday.

We'll have some frost in northwestern Pennsylvania and some patchy morning fog as well.

About ten degrees cooler than average for high temperatures on Monday.

But with high pressure dominating and lots of sunshine, we warm up as we get into the middle of the week with temperatures right around average on Thursday, that weak front moves through, bringing in some clouds and a light chance of some showers.

And then Friday, just a little bit cooler, but still close to average.

And we'll be back in a moment with week two trends.

Week two trends is our opportunity to peer beyond the extended forecast into the period 8 to 14 days out, which begins next Saturday and goes to two weeks from today to look for trends, temperatures above or below average.

And what about higher risks of precipitation?

I think in the week two period maybe starts with a day cooler than average, but there are signs later in the week that we'll have a bit of a warm up, as the jet stream will tend to migrate quite far north for this time of year, opening the door for temperatures to to go back up at least a little bit above average.

We're going to talk about temperatures being above or below average.

It helps to know what those numbers will be.

This is right in the middle of the 8 to 14 day period.

By this time, average highs southeast of the mountains will be below 80 and not to return until the first week of June in 2026.

So by this time, if the temperature were to reach the mid to upper 70s in central Pennsylvania, that would be a warmer than average day.

We're going to show you forecasts of pressure lines up around 20,000ft.

The winds tend to follow these lines, generally speaking, from west to east where they dip to the south.

These troughs tend to sponsor cooler than average weather and where they bulge to the northeast.

Ridges tend to sponsor warmer than average weather, at least at upper levels.

And this trough here is what's going to swing through over the weekend and drop our temperatures down a notch.

And you've already heard from Marissa in the extended forecast.

So I'm going to jump ahead to next Saturday where my part of the story begins.

By that time, notice how the red lines have separated from each other.

The green lines have separated from each other.

That's a sign that the solutions are diverging by quite a bit by this time.

The white line, by the way, is the average of the attendant, in this case, red lines.

I think by next Saturday, though, there's some agreement that the upper air flow will be northwesterly and that's a dry flow.

And I think we'll also probably sponsor a temperatures below average next Saturday.

After that though, the flow flattens out.

And now the red lines are tangling with the green lines.

Fairly high uncertainty.

So let's just average all the solutions together.

And on this chart the orange and yellow indicate temperatures above average and the blue indicate temperatures below average.

You don't see any of the blue across the lower 48 states.

And in fact, where these black lines are close together, that's where the jet stream is.

And it seems to be, generally speaking, in Canada.

And when the jet stream is that far north, that allows the possibility of getting somewhat warmer and somewhat more humid air back in here.

So that's what I'm going to go later in the week.

Two period with the jet stream so far north, pattern recognition suggests the temperatures here have a shot at going above average.

But I'm going to start us with one day below average.

It won't be cool.

That simply means temperatures below average and warm us up later in the period.

And I do think the northwest flow next weekend sponsors a higher confidence in dry weather.

Beyond that, though, precipitation chances are certainly uncertain.

So we'll start dry and on the cool side of average and then warm it up a bit.

That's it for week two.

Trends.

Back in a moment with more.

Well, it looks like if folks get skipped in the rain department tonight or tomorrow, it could be quite some time before our next chance of precip for the evening and overnight hours.

I think chances are going to be confined along into the west of I 99 one round early in the night, another round of showers later in the night.

A dry and mild night in southeastern Pennsylvania with increasing clouds through the overnight hours going into Saturday.

Unsettled but not a washout in the morning.

Hours in Western PA. That's where I think the best chance of some light rain is drying out by the afternoon.

Ahead of the cold front, it will become quite warm and muggy in southeastern PA, likely dry through much of the day there before showers and thunderstorms develop in the afternoon to evening hours.

Central PA a bit of a mixed bag, but I would say scattered light rain is the theme.

Maybe around in the morning, around in the afternoon as well, but not a washout there.

And then going into Sunday feeling like fall.

Most of us staying dry.

Highs anywhere from the mid 60s to low to mid 70s.

Filippo really the pick of the weekend for us.

Well looking forward to that gorgeous Sunday.

Thank you so much Carl for that forecast.

And thank you all at home for tuning in to another week of Weather World.

Stay tuned for Monday where we have an alumnus of the show coming back as a