Meteorology and atmospheric science at Penn State.

This is weather world.

Good evening and welcome to Weather World on this Thursday, January 22nd.

I'm your host, Matthew Carlson joined alongside our forecaster Christian, Sloane and Christian.

Quite a lot to talk about in tonight's forecast.

Yeah, absolutely.

We've had the cold air around for much of the week.

A little bit of a warmer day today, but going right back into the icebox tomorrow and then big time snow possible this weekend.

All right.

Well looking forward to hearing more in your forecast.

Stick around on tonight's show as we've got a special edition of Snow Risk, including some team coverage from all of us here in the Weather Communications group.

But first, here's Christian at the wall.

Yeah, thanks very much, Matthew.

And like we mentioned, we have that high impact storm coming in this weekend.

But last night we had even a little bit of a prelude to some some of the snowfall with just some light accumulations across some parts of the state, mainly across central and northwestern Pennsylvania.

As a weak disturbance came through, dropped at least a coating to two inches of snowfall in some areas, this blue contour here representing at least two inches in this area, so some light accumulations making for some slick travel, and this will only amplify and become more wintry as we head into the weekend with a large storm on the horizon.

But today it was a little bit of a different theme across there.

As that disturbance passed through, we had some warm air that came up, especially across southeastern Pennsylvania, that brought in temperatures upwards of 50 degrees all the way down in Philadelphia and into the 40s across much of southeastern Pennsylvania.

I think that will be some of the highest temperatures we see over the next week to two weeks, even across this area, as it looks like after this weekend, a very cold air mass sticks around for quite a while, a bit cooler up towards the northwest plateau, and we'll be expecting a front that will eventually come through that area as we head towards the day tomorrow.

On Friday, that will drop temperatures quite rapidly for much of Pennsylvania, below the levels we saw today on the satellite and radar image, you saw this westerly flow, some of the residual snowfall, even over the Laurel Highlands that you can make out in the visible satellite image here that fell last night.

And as we zoom out, we can see this broader pattern behind the system that came through yesterday of this westerly flow.

The next front that's going to come through tomorrow are Arctic front looks up towards the north and west, and we'll show that a bit later.

And that will really bring in the cold shot of air that will fuel all this snowfall and wintry precipitation.

As we get into this weekend, we can see the wind gusts behind that, producing wind gusts up to 30mph.

This will stick around as these next couple fronts come through into the day tomorrow and even into early Saturday.

So they'll be quite a quite a bite to the wind.

And a wind chill that will drop feels like temperatures below zero at times throughout much of this period, in advance of the storm that's coming in, starting on later Saturday across much of the region, the National Weather Service has issued winter storm watches today.

These run out through the day on Monday, and these will likely be upgraded to warnings across the board as we go over the next 24 to 48 hours or so.

Zooming out, we can see the broader satellite and radar image with some of the precipitation behind the system that came through yesterday.

Continuing lake effect snowfall along the Great Lakes, but really dry across much of the area as the pieces for the next storm start to organize out across the western United States, you can see the large trough that's slowly beginning to dig in across much of the lower 48 here, with this big dip in the jet stream, you can see really in this this outline almost of the temperature contours.

There's about a 100 degree difference in temperatures between Brownsville, Texas and International Falls this afternoon, showing the sharp temperature contrast and what's going to drive some of the instability and fuel in the system as it eventually develops for this weekend.

So we can take a look at the evening surface map here.

This is the key Arctic front and this cold front here that's going to pass through as we head into the day on Friday.

Tomorrow afternoon we'll see that pass by and you'll see the wind pick up.

And eventually an Arctic high pressure system pass in to the northwest behind that.

Eventually, the system that we'll be talking about this weekend will have more information on just a little bit.

We'll start forming across the south western portion of our area here.

And this really broad precipitation shield, you can see this front that's very far off to the south of us here, that will allow for this storm to pick up a lot of moisture from the Gulf of Mexico.

Here's a look at one of our high resolution forecast models.

You can see the cold conditions, the front that comes through during the day tomorrow with some biting wind chills and temperatures low temperatures likely below zero for many in the northwest.

As we start the day on Saturday before precipitation comes onto our doorstep by the afternoon on Saturday.

Here's a look at the forecast for tonight.

Really just a dry, cold and breezy day with a few snowflakes as you go up across the northwest plateau.

Low temperatures for many tonight in the teens to middle 20s before the cold weather really comes in tomorrow.

Behind that front, cold weather advisory is in effect for many, with wind chills likely up to negative ten degrees for some across the state.

By tomorrow evening, temperatures actually falling into the single digits and below zero by tomorrow night across western Pennsylvania.

And on Saturday, the major storm nears with a frigid start, high temperatures only in the single digits across the northern tier and only into the teens with a lot of cloudy conditions.

Good day to finalize preparations on Saturday.

More information on the storm coming up next.

Good evening and welcome to this special edition of Snow Risk.

I'm Marissa Ferger, and we're here tonight because a major winter storm is going to impact a big part of the country.

I'll be joined by Jon Karl Schneider and Rob Lydick.

And behind the scenes, we had help and collaboration from Bill Syrett, Ben Reppert and Kyle Imhoff.

So to start things off tonight, we are going to look at the big picture of who is going to be impacted by this and what the storm set up is.

And with that, I'm sending it over to Jon.

Thanks, Marissa.

And the National Weather Service has certainly acknowledged the widespread nature of this of the storm with its winter weather alerts, winter storm warnings in pink, winter storm watches in blue purple.

There indicates an ice storm warning stretching all the way from the desert southwest into the northeast.

National Weather Service Right on top of this, this is a National Weather Service forecast map for Saturday morning around 8 a.m.

You want a winter storm, you need cold, you need moisture, and you need a reason for the air to go up.

Well, the cold air will be supplied by an extensive area of high pressure that will move into the northern part of the country.

I'll show you the moisture in just a moment.

But this front will also play a role because fronts are places where air goes up.

And when we look at the map here, this is also Saturday morning at 8 a.m.

this black circle here, that's the area of high pressure.

The wind barbs you see here, these wind particles, that's winds about 5000ft above the ground.

And they're coming north out of the Gulf of Mexico.

The greens are high relative humidity, air.

And this warm, relatively moist air coming northward is running up and over this shield of cold air to the north.

And it's a pretty fast flow up around 5000ft.

And by Sunday morning that will be directed right into Pennsylvania.

Center of low pressure will organize in the South.

It will move northeastward to be poised off the East coast by Sunday evening.

And it's the proximity of that center of low pressure that might bring the potential for a little bit of mixing here in Pennsylvania.

And for more on that, here's Karl.

And thanks very much, John.

The reason that the position of the surface low is so important is because of the impacts on the thermodynamic environment that we're talking about the temperatures here.

And so I have a couple graphics to show you.

The first is a vertical profile of temperature with height.

This is a forecast for Philadelphia on Sunday afternoon.

And while you can see that the near surface temperatures will be well below freezing aloft, it looks like what we call a warm nose or some increased temperatures with height will cause temperatures to approach or even exceed freezing.

And if that occurs, sleet will mix in.

This looks to be most likely in southeastern Pennsylvania, and if this happens, this will could drastically reduce snow totals depending on how early this transition to sleet happens.

If it does at all, we'll contrast that with what's expected in northwest Pennsylvania and central PA as well.

This is astounding from Erie around the same time, and you can see how far this profile is away from freezing, indicating that the snow should be dry and powdery in nature for areas in central and western Pennsylvania.

So for more info about the specifics of this storm, here's Rob.

Thanks a bunch, Karl.

Let's talk about storm timing.

We think the Arctic area of high pressure will be centered over the northeast.

By the time we get to Saturday evening, the onset of the precipitation likely beginning Saturday night.

By the time you wake up on Sunday morning, I think we'll see a good dump of snow at that point across Pennsylvania, watching two distinct areas of low pressure as this all pushes northeastward.

And that will actually nudge this one offshore, nudging that freezing line ever so close to southeast Pennsylvania, as Carl just talked about something we're concerned with the potential for mixing, especially in southeast Pennsylvania or some areas south of the Turnpike, that snow continues to fall at a pretty good rate as we go into Sunday night.

By the time we get to Monday, more uncertainty on just how quickly the precipitation ends.

This model, the European, actually quickly wraps things up Monday morning.

Others leave that snow falling into at least the middle part of the day on Monday, and the snow pack lingers as we go into early next week.

So talking about uncertainty here, our confidence levels, well, the storm begins Saturday night.

We feel good about that.

We feel that the fluff factor is still certainly at play, as Carl talked about in northwest Pennsylvania.

And of course, statewide impacts, some of which will be significant.

That's where our confidence lies, where we're less confident in, well, the storm end time will last through the day on Monday or wrap up quicker.

Mixed potential south of the Turnpike and specific accumulation amounts.

But no matter which way you shake it, the National Weather Service has a winter storm watch through the entirety of Pennsylvania into Monday afternoon.

Back to you, Marissa.

Thanks, Rob.

It's been a while since we've seen the entire Commonwealth under a winter storm watch, and it does look like everyone could see wintry precipitation on Sunday.

And what are we expecting?

Well, let's look at the map right now in northwestern Pennsylvania.

It looks like it's going to be a plowable snowfall from the Alleghenies through the Pittsburgh Metro.

We could see double digit snow.

It is possible, but where it's more likely is from the Laurel Highlands, up through the Capital Region, the central mountains, into the endless mountains down to the Poconos and the Lehigh Valley.

That is where we're going to have the best chance for double digit snowfall.

The biggest question mark is who is going to see the mixed precipitation.

Karl already alluded to that earlier.

Anywhere from south central Pennsylvania down into the Philly metro area, mainly south of I-76.

That's where we could see that potential for mixing.

So what can you do now to prepare?

The storm is going to start late on Saturday.

It's Thursday night.

Well, get everything in order.

You want to get your supplies before the snow starts.

Any food, any prescriptions, batteries, baby supplies, or if you need any fuel, you want to be prepared for power outages.

So on Saturday, it's a good idea to charge your devices and make sure you have some batteries and candles and matches on hand.

If you are going to be using a generator, make sure you do it outdoors.

You never want to run a generator in an enclosed area, and if you are going to run one, have some carbon monoxide detectors.

Make sure their batteries are functioning.

That is a big safety issue.

Something else to remember.

This is not just about snowfall.

It is going to be extremely cold throughout the storm and afterwards.

So if you have any pets, make sure they're indoors.

And if you work on a farm, if you have farm animals, move them to a sheltered area and make sure they have water and their food nearby and that that water does not freeze.

I think a big thing to remember with this system is that it's not just about the snow on Sunday.

It is going to be dangerously cold throughout the weekend and following the storm.

In fact, it may not be until early February where Pennsylvania or anywhere in Pennsylvania sees above freezing temperatures.

So a very cold stretch in store.

We'll be back in a moment with more.

We'll have dry conditions over the next 48 hours or so for many to continue preparations for that storm.

But it will be cold, however, especially as an Arctic front approaches the area.

Tonight, we'll see temperatures down into the teens across the Northwest Plateau and the warmest spots across the southeast, getting up into the upper 20s for low temperatures, with partly cloudy skies for many across the state tonight.

And on Friday, that Arctic front will cross through its approximate position as we go throughout the middle of the day.

That will drive temperatures down throughout much of the afternoon in western Pennsylvania.

I think you're dropping through the single digits and even below zero by the time we get towards Friday evening across the northwest, a bit milder across the southeastern portion of the state with some sunshine tomorrow, but it drops down for everyone by the time we get towards Saturday.

As that storm approaches Pennsylvania from the southwest, a frigid start with temperatures below zero for many across the northern tier on Saturday, with wind chills well below zero.

Back to you, Matthew.

Thank you very much, Christian, and thank you for coming tonight.

Come back tomorrow for an update on the weekend snowstorm and the Friday forecast frenzy taking us into February.

Have a great